OXYGEN

1

Oxygen

O

2

[7782-44-7]

O

2

(MW 32.00)

InChI = 1/O2/c1-2
InChIKey = MYMOFIZGZYHOMD-UHFFFAOYAM

(oxidizing agent for many organic systems, including, most
commonly, organometallic compounds, carbon radicals, and

heteroatoms such as sulfur)

Physical Data:

mp −218

◦

C; bp −183

◦

C; d 1.429 g L

−1

(0

◦

C),

1.149 g L

−1

(−183

◦

C).

Solubility:

sol to some extent in most solvents. Selected data,

expressed as mL of O

2

(at 0

◦

C/760 mmHg) dissolved in 1

mL of solvent when the partial pressure of the gas is 760
mmHg, are as follows: Me

2

CO (0.207/18

◦

C), CHCl

3

(0.205/

16

◦

C), Et

2

O (0.415/20

◦

C), EtOAc (0.163/20

◦

C), MeOH

(0.175/19

◦

C), petroleum ether (0.409/19

◦

C), PhMe (0.168/

18

◦

C), H

2

O (0.023/20

◦

C).

Form Supplied in:

dry gas; dilutions in Ar, He, or N

2

;

18

O

2

;

17

O

2

.

Handling, Storage, and Precautions:

of itself, oxygen gas is es-

sentially nontoxic. However, it will support and vigorously in-
crease the rate of combustion of most materials. It may ignite
combustibles and can cause an explosion on contact with oil
and grease. The potential for autoxidative formation of explo-
sive peroxides (e.g. with Et

2

O) should always be borne in mind.

Original Commentary

A. Brian Jones
Merck Research Laboratories, Rahway, NJ, USA

Oxygenation of Carbanions and Organometallic Compo-

unds. Many organometallic species react with triplet oxygen to
form the corresponding hydroperoxides,

1,2

although the products

are more usually reduced in situ or during workup to afford alco-
hols as the isolated products. A number of other sources of elec-
trophilic oxygen have been developed (e.g. Oxodiperoxymolyb-
denum(pyridine)(hexamethylphosphoric triamide) (MoOPH),
sulfonyloxaziridines) and compete for this niche, but no sin-
gle reagent is universally preferable. As carbon anion equiva-
lents, Grignard reagents are optimal for simple hydrocarbons,

2

but

organolithiums are more frequently employed. The potential
for radical-mediated oxidative dimerization can constrain utility
(particularly for aryl organometallics). Useful oxygenations of
alkyl,

3

vinylic,

4

allylic,

5

benzylic,

6

and aryl (eq 1)

6

organolithium

compounds have been reported. 1,1-Diorganometallics give the
corresponding carbonyl derivatives (eq 2).

7

(1)

s

-BuLi, TMEDA

OMe

CONH

2

OMe

CONH

2

OH

O

2

, –78 °C

46%

C

6

H

11

SnMe

3

ZnBr

OEt

C

6

H

11

CHO

OEt

(2)

O

2

(air), TMSCl

THF, –5 °C

Effective oxygenation of enolate anions is generally restricted

to tertiary centers where over-oxidation is not possible.

8

Nonethe-

less, ketones (eq 3),

9

esters/lactones,

8

amides/lactams (eq 4),

10

and carboxylic acids

8

can all be usefully α-hydroxylated. In most

cases the intermediate α-hydroperoxides are reduced in situ (usu-
ally with Triethyl Phosphite),

11

although they can be isolated if

desired.

12

The small size of the electrophile and the potential for

radical involvement

8

do not encourage stereochemical chastity in

these processes, but where sufficient bias exists, good discrim-
ination can be observed (see eqs 3 and 4). A slightly different
approach uses enolates derived from aqueous base treatment.
These species have been usefully hydroxylated where there was
little or no ambiguity in the direction of enolization

8

and this pro-

cess forms the basis for a surprisingly effective catalytic, enantio-
selective oxygenation (eq 5).

13

(3)

O

2

, THF

O

–

K

+

S

S

O

H

S

S

OH

H

from anionic oxy-Cope

P(OEt)

3

NEt

O

BnO

H

H

Ph

NEt

O

BnO

OH

H

Ph

(4)

LHMDS

O

2

, P(OEt)

3

THF, 0 °C

60%

O

2

, P(OEt)

3

aq NaOH

(5)

Cl

OMe

O

Cl

OMe

O

OH

N

+

N

CF

3

HO

cat =

Br

–

79% ee

5 mol % cat

95%

In cases where the activating group is also a leaving group,

oxygenation can provide the corresponding carbonyl compound.
Thus oxidative decyanation can be effected under either phase
transfer

14

or anhydrous conditions (eq 6).

15

The latter procedure

is more general, although it does require treatment with Tin(II)
Chloride and base to reduce and fragment the α-hydroperoxide,
and this method is not effective for the primary nitrile to
aldehyde conversion. α,β-Unsaturated nitriles generally react at
the α-position to give α,β-unsaturated ketones.

15

t-

BuO

CN

t-

BuO

O

(6)

LDA, O

2

THF, –78 °C

then SnCl

2

and basic w/u

70%

Avoid Skin Contact with All Reagents

2

OXYGEN

Oxygenation of sulfone anions and the consequent desulfonyla-

tion is frequently effected with the MoOPH reagent. In some cases,
however, molecular oxygen has proved effective where MoOPH
failed.

16

This perhaps illustrates a functional advantage over more

bulky reagents and a counterpoint to the stereochemical disadvan-
tages (see above). It should be noted that one such attempt resulted
in a minor explosion

17

although, of course, any reaction involv-

ing peroxides bears this possibility. A similar process, preceded
by nickel transmetalation, demonstrated the oxidation of the C–Ni
bond, but the synthetic advantage is not clear.

18

However, this re-

port did demonstrate the conjugative oxygenation of an allylic
sulfone anion to give a γ-hydroxy sulfone.

Oxygenation of phosphorus-stabilized anions also produces

the corresponding carbonyl compounds. The anions derived
from phosphonates

19

(eq 7)

20

(including α-heteroatom substituted

phosphonates)

19

and phosphine oxides

21

react smoothly with

oxygen. Similarly, phosphorane ylides are readily oxidized.

22

In

all these cases, however, the reaction of primary substrates suffers
from competing self-condensation, giving alkenes.

22

It should be

noted that a two-stage procedure involving the reaction of phos-
phonate anion with chlorodimethyl borate followed by oxidation
with m-Chloroperbenzoic Acid has been advocated as a more
efficient method

23

(and, interestingly, allows isolation of the

intermediate hydroxy phosphonate).

N

O

P

O

Ph

OEt

OEt

N

O

O

Ph

(7)

BuLi, O

2

THF, –78 °C

70%

Oxygenation of Carbon Radicals. Not surprisingly, triplet

oxygen reacts rapidly with carbon centered radicals.

24

Classical

autoxidation is the most obvious example of this behavior. Tra-
ditionally, autoxidation refers to hydroperoxide formation from
alkanes, aralkanes, alkenes, ethers, alcohols, and carbonyl com-
pounds, where the initiating homolysis is induced thermally or
photochemically.

25,26

There is an extensive literature concern-

ing these processes dating back many years. While very impor-
tant commercially, they are generally too promiscuous to be of
wide synthetic value, particularly when dealing with complex
molecules. Interestingly, however, a deformylative hydroxylation
of an allylic neopentyl aldehyde has been observed that bypasses
the classical autoxidative fate of aldehydes (eq 8).

27

O

CHO

H

HO

O

OH

H

HO

(8)

O

2

, PPh

3

50 °C

37%

Radical oxygenation is most valuable where there is more

strict control over the site of radical formation and subsequent
oxygenation. Good stereochemical control is, of course, not
usually achieved, although exceptions can be found in most cases.
The mild and controlled methods of radical generation that have
seen much use in synthesis are readily applicable to oxygenation.
The thermal or photochemical decarboxylation of the esters of
thiohydroxamic acids,

28

or their room temperature decomposi-

tion in the presence of tris(phenylthio)antimony

29

(i.e. Barton’s

methodology), can be intercepted by triplet oxygen to generate
the nor-alcohols. The addition of heteroatom radicals to alkenes
can provide the source of carbon centered radicals for trapping.
An interesting example of oxygenation initiated by phenylthio or
phenylseleno radical addition to vinylcyclopropanes showcases
the use of this methodology (eq 9).

30

Here, instances of mod-

erately successful stereocontrol in the C–O bond forming step
were noted. This transformation also demonstrates the potential
of the initially formed hydroperoxy radical to participate in fur-
ther steps (where higher levels of stereochemical discrimination
are observed as a consequence of the intramolecular nature of the
radical trapping). Samarium(II) Iodide induced radical processes
have been quenched with oxygen to provide hydroxyl functional-
ized products.

31

(9)

PhSe

CO

2

Me

CO

2

Me

O

O

CO

2

Me

O

O

CO

2

Me

PhSe

(PhSe)

2

, AIBN

O

2

, 0 °C

α:β = 6.5:1

One of the most prevalent uses of molecular oxygen in modern

synthesis is for oxidative demercuration.

32

Carbon radicals gen-

erated by the reduction of organomercurials with borohydride are
efficiently trapped by oxygen, most frequently in DMF solution, to
give hydroperoxides which are reduced under the reaction condi-
tions to generate the corresponding alcohols directly.

33

The alkene

oxymercuration–oxidative demercuration sequence is commonly
practised (usually through a β-alkoxymercury species, since β-
hydroxy fails

33

), particularly where the oxymercuration is an

intramolecular cyclization (eq 10).

34

Typically, any stereocontrol

observed in the oxymercuration (or other C–Hg bond forming
step) is effaced in the oxygenation (as in eq 10).

(10)

O

ClHg

NC

O

HO

NC

O

HO

O

O

H

O

O

H

HO

NC

OH

HgCl

Hg(OTFA)

2

O

2

, NaBH

4

DMSO

Hg(OTFA)

2

O

2

, NaBH

4

DMSO

single isomer

1.6:1

70%

DMF, KCl

44%

DMF, KCl

A list of General Abbreviations appears on the front Endpapers

OXYGEN

3

Oxidation of Organoboranes.

Boranes, most frequently

accessed by hydroboration of alkenes, can be oxidized by triplet
oxygen.

35,36

If the oxidation is carried out in fairly concentrated

solution (˜ 0.5 N) at 0

◦

C, intermolecular redox reaction of the

intermediate diperoxyborane is facilitated and workup provides
the corresponding alcohol.

36

While this is quite efficient, Hydro-

gen Peroxide is more commonly used in synthetic applications.
This is partly for convenience, but also a consequence of stereo-
chemical issues. The oxidation with H

2

O

2

occurs with retention

of configuration at the carbon center. The radical characteristics of
the dioxygen reaction generally lead to at least partial racemiza-
tion. That this stereochemical corruption is not always complete
is an indication of the uncertainty about the mechanism.

35

In-

terestingly, rhodium(III) porphyrin has been shown to promote
stereoselective oxidation in the dioxygen procedure (eq 11).

37

In

dilute solution (0.01–0.05 N) the intermolecular redox process is
suppressed and diperoxyboranes are produced. Oxidation of the
third B–C bond with H

2

O

2

or peroxy acid and workup allows

isolation of the corresponding alkyl hydroperoxides.

36

Alterna-

tively alkyl hydroperoxide formation is facilitated by the use of
alkyldichloroboranes.

36

This is one of the most convenient

approaches to this functionality. The oxygen mediated approach
to alcohols may be more convenient than H

2

O

2

for radiolabeling;

17

O (eq 12) and

15

O alcohols have been prepared in this way.

38,39

OH

O

2

B

X

X

OH

(11)

O

2

single isomer

4:1

(OEP)RhH

NaBH

4

S

BH

3

S

OH

(12)

17

17

O

2

Heteroatom Oxidation.

Oxidation of nitrogen function-

ality with oxygen, while well precedented.

40

and of continuing

interest,

41,42

does not generally represent the method of choice

for those processes of synthetic significance. However, a report
of a mild procedure for the oxidation of silylamines to carbonyl
compounds bears some synthetic potential (eq 13).

43

Oxidation

of phosphorus functionality by oxygen can be quite facile.

44

For

example, tertiary phosphines are very readily oxidized to their
phosphine oxides, and secondary chlorophosphines can give the
phosphinic acids.

44

Perhaps the most common heteroatom air oxi-

dations are those of Group 16 RX–H bonds to their corresponding
dimers ((RX)

2

) and particularly the thiol to disulfide oxidation.

45

This, of course, is related to the importance of the disulfide bond to
peptide and protein secondary structure. One example that reflects
current interest in the control of multiple disulfide bond forma-
tion in synthetic peptides is given in eq 14.

46

Oxidation may be

promoted by heavy metal ions.

45

Higher oxidations (for exam-

ple sulfide to sulfoxide) are best performed with other reagents
(oxone, peroxy acid, etc.).

N

TMS

H

O

(13)

BuLi, air

–78 to –40 °C

then SiO

2

89%

OH

SH

SH

OH

S

S

S

(14)

S

SH

SH

air

pH 8

major isomer

L

G

G

L

G

G

G

L

G

L

G

G

T

R

T

S

C

Q

N

C

W

R

C

S

Q

N C

A

S

V

C

Q

A

C

W

C

S

Q

N C

N

V

Other Uses. The oxidative dimerization of organometallics,

alluded to above, is particularly prevalent for organocuprates,

47

although not totally unavoidable.

48

In fact it is efficient enough

to be regarded as a synthetic strategy and has been used as such
(eq 15).

49

Baeyer–Villiger oxidations generally employ peroxy

acids, but a recent report indicates that 1 atm of oxygen can
effect the rearrangement even in the absence of either metal
catalysts or light.

50

Epoxidation by oxygen is possible

51

but,

of course, is not usually the method of choice for laboratory
synthesis.

(15)

MeO

MeO

MeO

MeO

OTBS

OMe

OTBS

OMe

MeO

MeO

OTBS

OMe

X

OR

1

OR

2

OR

1

/R

2

R

1

= TBS; X = Li

+

R

2

= TBDPS; X = CuCNLi

O

2

, –131 °C

58%

There is a vast literature concerning metal-catalyzed oxida-

tive processes involving molecular oxygen,

52

of which only a

fraction have seen synthetic use. Many metal catalysts behave
as oxygen fixing species, that deliver oxygen to the substrate
through a peroxo complex. Reports frequently concern experi-
mental systems, probing substrate reactivity and/or asymmetric
induction. The function of oxygen in metal-catalyzed oxidations
is not necessarily that of a reagent. Thus, for example, in the
Wacker oxidation of terminal alkenes it operates as a re-oxidant
for copper(II) chloride which in turn is a re-oxidant for the Pd

II

species. All of these applications are best regarded as functions
of the metal component and, for this reason, are not discussed
here.

Avoid Skin Contact with All Reagents

4

OXYGEN

First Update

Jun Wang & Ashton T. Hamme, II
Jackson State University, Jackson, MS, USA

Oxygenation of Carbanions and Organometallic Compo-

unds. Some recent oxygenation reactions involving organometa-
llic reagents have involved the synthesis of alcohols and alkyl
hydroperoxides. Straight chain, cyclic, and benzyl alcohols were
synthesized in good yields through the reaction of organozinc
compounds with oxygen in THF in the presence of 1 equiv of
HMPA.

53

This reaction sequence was also used towards the syn-

thesis of a chiral alcohol as a 1:1 mixture of diastereomers (eq 16).

ZnBu

n-

C

4

H

9

n

-C

5

H

11

HMPA

OH

n-

C

4

H

9

n

-C

5

H

11

dry air

*

*

(16)

An analogous organozinc oxygenation in THF without HMPA

was used to synthesize halogen, ester, sulfonamide, and silicon-
containing alcohols.

54,55

Oxygenation of a geminal trimethyl-

silyl organozinc compound afforded the corresponding aldehyde
(eq 17). The incorporation of different workup conditions can give
rise to the isolation of either alcohols or alkyl hydroperoxides
during the oxygenation of organozinc compounds in perfluoro-
hexane (PFH) (eq 18).

54

–

56

OBn

SiMe

3

ZnX

OBn

CHO

O

2

, THF

− 10

°

C, 0.5 d

cis

:trans 17:83

(17)

ZnBr

OOH

64%

O

2

, PFH

− 78

°

C

(18)

Oxygenation of Carbon Radicals. Carbon-centered radicals

generated from the corresponding alkyl halide and radical initia-
tors can be trapped with molecular oxygen to give rise to alco-
hols. Radiolabeled

18

O and

17

O alcohols were prepared through

the aerobic oxygenation of carbon radicals formed through a Bu

2

(t-Bu)SnCl–sodium cyanoborohydride catalytic system (eq 19).

57

A similar method was used to oxygenate the carbon radical gener-
ated after the carbocyclization of an olefinic alkyl halide (eq 20).

57

O

OAc

AcO

OAc

OMe

H

18

O

OMe

I

O

OAc

AcO

OAc

(19)

NaBH

3

CN (2 equiv)

t

-BuOH, 60

°

C

88%, >85 isotopic purity

Bu

2

(t-Bu)SnCl (5 mol

%)

AIBN (1 mol

%)

18

O

2

(2 equiv, 99 atom

%)

O

OMe

I

O

OMe

OH

(20)

Bu

3

SnCl (5 mol

%)

AIBN (1 mol

%)

O

2

(1.5 equiv)

NaBH

3

CN (2 equiv)

t

-BuOH, 60

°

C

83%

Radical oxygenation of 2-deoxy-2-iodo hexopyranosides was

achieved through a procedure involving AIBN, Bu

3

SnH, and O

2

in toluene at 60

◦

C (eq 21).

58

Either a higher yield or selectiv-

ity was achieved with this method when compared to similar
methods at room temperature

59

or from the analogous chloromer-

curic starting material.

60

An oxygen quench was used after

the Bu

3

SnCl/AIBN/sodium borohydride-initiated cyclization of

iodo allyoxy substituted tetrahydrofuran and pyran compounds to
afford the corresponding bicyclic alcohols (eq 22).

61

air, toluene, 60

°C

Bu

3

SnH, AIBN

84%

O

TBSO

TBSO

OMe

I

TBSO

O

TBSO

TBSO

OMe

OH

TBSO

O

TBSO

TBSO

OMe

TBSO

OH

+

4:1

(21)

O

O

OTBS

TBSO

TBSO

I

Ph

O

TBSO

TBSO

TBSO

H

H

H

Ph

OH

(22)

AIBN, NaBH

4

, BuSnCl, O

2

84%

The aerobic reductive oxygenation of an alkyl halide using

Bu

2

(t-Bu)SnH in air with ultrasound irradiation affords the alkyl

hydroperoxides in moderate yield but good selectivity.

62

Mild

reductive work-up of the peroxy-radical intermediate without
overreduction of the oxygen-oxygen bond enabled the isolation
of the alkyl hydroperoxide over the alcohol.

Oxidation of Organoboranes. A variety of diethylorgano-

boranes were oxidized with oxygen when bromoperfluooctane
(BPFO) was used as a solvent.

63

A number of functional groups,

including halides, TIPS-ether, sulfonamide, esters, and mal-
onate survived the relatively mild reaction conditions. Secondary
diethylorganoboranes were oxidized with retention of configu-
ration. An insertion mechanism rationalizes the stereochemical

A list of General Abbreviations appears on the front Endpapers

OXYGEN

5

outcome of the reaction due to the high reactivity of the boron-
ethyl bond towards oxygen (eq 23).

OH

H

OH

H

OH

(23)

1. Et

2

BH

79%

2. O

2

, BPFO

(major isomer, 9:1)

The oxidation of alkylboronic esters to afford alcohols has also

been achieved in high yields using triethylamine and molecular
oxygen in THF.

64,65

This method of oxidizing alkylboronic esters

shows a high degree of regioselectivity for terminally substituted
alkylboronic esters (eq 24) and stereoselectivity for secondary
alkylboronic esters (eq 25). The oxidation of these alkylboronic
esters follows both free radical and polar mechanistic pathways
(eq 26).

64,65

O

2

Et

3

N

N

N

H

3

CO

HO

B

O

O

N

N

H

3

CO

HO

HO

62%

(only one isomer detected)

(24)

O

2

Et

3

N

B

O

O

OH

OH

+

10:1

(25)

85%

O

2

, Et

3

N

then H

2

O

B

O

O

HO

OH

+

90%

2:1

(26)

Heteroatom Oxidation. Although the oxidation of nitrogen

or sulfur functionalities is precedented,

40

the most recent oxi-

dations of these heteroatoms using molecular oxygen usually
involve either a transition metal catalyst

66−68

or the conversion of

an aldehyde into a peracid.

69

In these cases, molecular oxygen is

not involved in the direct heteroatom oxidation. Therefore, these
and other similar examples will not be discussed here.

Other Uses. A number of oxygenative radical cyclizations

involve cobalt catalysts in the presence of oxygen. Some meth-
ods involve the oxygenolysis of the cobalt-carbon bond

70

while

other methods use a catalytic amount of a cobalt complex, and the
resulting carbon radical is oxygenated.

71,72

Carbafuranose com-

pounds were synthesized from 6-iodo-hex-1-enitols through Co
(salen)-catalyzed oxygenative radical cyclization (eq 27).

73

Perfluorinated ruthenium and nickel complexes were used to syn-
thesize epoxides, sulfones or sulfoxides, and carboxylic acids from
the analogous alkene, sulfide, and aldehyde precursors in high
yield using a biphasic organic solvent/perfluorohydrocarbon
oxygen saturated system.

74

EtOH, NaOH, NaBH

4

OBn

OH

O

O

OBn

O

O

OH

I

OBn

O

O

O

2

, Co(salen), 40

°

C

(27)

80%

+

1.2:1

Baeyer-Villiger

75,76

and alkene oxidations

76

were performed

with molecular oxygen and benzaldehyde. The active oxidant is
peroxybenzoic acid, which is generated in situ through the reac-
tion of oxygen with benzaldehyde. The synthesis of functionalized
α

,β-unsaturated butenolides was achieved through an oxidative re-

arrangement of 6-methoxypyran-2-one compounds involving the
oxidation of a ketene intermediate with molecular oxygen.

77

Oxygen has also been used as a secondary oxidant in 2,2,6,

6-tetramethyl-piperidyl-1-oxo (TEMPO),

78,79

N

-hydroxyphthal-

imide (NHPI),

80

transition metal-mediated oxidations.

81,82

Copper-free palladium-catalyzed asymmetric aerobic Wacker
cyclizations were also achieved where oxygen served as the reoxi-
dant of the palladium complex.

83

Since molecular oxygen serves

as a secondary oxidant and not the primary oxidant for other tran-
sition metal-based oxidations, no other examples will be discussed
at this juncture.

Related Reagents. Copper(I) Chloride–Oxygen; Diethylzinc–

Bromoform–Oxygen;

Iron(II)

Sulfate–Oxygen;

Oxygen–

Platinum

Catalyst;

Singlet

Oxygen;

2,2,6,6-Tetramethyl-

piperidyl-1-oxo-oxygen;

N

-Hydroxyphthalimide-oxygen;

Osmium

Tetraoxide–Copper(I)

Chloride–Oxygen;

Ru-

Hydrotalcite Catalyst–Oxygen.

Avoid Skin Contact with All Reagents

6

OXYGEN

1.

Sosnovsky, G.; Brown, J. H., Chem. Rev. 1966, 66, 529.

2.

Wardell, J. L. In Comprehensive Organometallic Chemistry; Wilkinson,
G., Ed.; Pergamon: Oxford, 1982; Vol. 1, Chapter 2.

3.

Warner, P.; Lu, S.-L., J. Org. Chem. 1976, 41, 1459.

4.

Panek, E. J.; Kaiser, L. R.; Whitesides, G. M., J. Am. Chem. Soc. 1977,
99

, 3708.

5.

Takahashi, T.; Nemoto, H.; Kanda, Y.; Tsuji, J., J. Org. Chem. 1986, 51,
4315.

6.

Parker, K. A.; Koziski, K. A., J. Org. Chem. 1987, 52, 674.

7.

Knochel, P.; Xiao, C; Yeh, M. C. P., Tetrahedron Lett. 1988, 29, 6697.

8.

Jones, A. B., Comprehensive Organic Synthesis, 1991, 7, Chapter 2.3.

9.

Paquette, L. A.; DeRussy, D. T.; Pegg, N. A.; Taylor, R. T.; Zydowsky,
T. M., J. Org. Chem. 1989, 54, 4576.

10.

Kim, M. Y.; Starrett, Jr., J. E.; Weinreb, S. M., J. Org. Chem. 1981, 46,
5383.

11.

Gardner, J. N.; Carlton, F. E.; Gnoj, O., J. Org. Chem. 1968, 33, 3294.

12.

Bailey, E. J.; Barton, D. H. R.; Elks, J.; Templeton, J. F., J. Chem. Soc.
1962, 1578.

13.

Masui, M.; Ando, A.; Shioiri, T., Tetrahedron Lett. 1988, 29, 2835.

14.

Donetti, A.; Boniardi, O.; Ezhaya, A., Synthesis 1980, 1009.

15.

Freerksen, R. W.; Selikson, S. J.; Wroble, R. R.; Kyler, K. S.; Watt, D.
S., J. Org. Chem. 1983, 48, 4087.

16.

Yamada, S.; Nakayama, K.; Takayama, H.; Shinki, T.; Suda, T.,
Tetrahedron Lett. 1984

, 25, 3239.

17.

Little, R. D.; Myong, S. O., Tetrahedron Lett. 1980, 21, 3339.

18.

Julia, M.; Lauron, H.; Verpeaux, J. N., J. Organomet. Chem. 1990, 387,
365.

19.

Mikolajczyk, M; Midura. W.; Grzejszczak, S., Tetrahedron Lett. 1984,
25

, 2489.

20.

Tsuge, O.; Kanemasa, S.; Suga, H., Chem. Lett. 1986, 183.

21.

Davidson, A. H.; Warren, S., J. Chem. Soc., Chem. Commun. 1975, 148.

22.

Bestmann, H. J., Angew. Chem., Int. Ed. Engl. 1965, 4, 830.

23.

Kim, S.; Kim, Y. G., Bull. Korean Chem. Soc. 1991, 12, 106.

24.

Maillard, B.; Ingold, K. U.; Scaiano, J. C., J. Am. Chem. Soc. 1983, 105,
5095.

25.

Swern, D. In Comprehensive Organic Chemistry; Barton, D. H. R., Ed.;
Pergamon: Oxford, 1979; Vol. 1, Chapter 4.6.

26.

Crabtree, R. H.; Habib, A., Comprehensive Organic Synthesis 1991, 7,
Chapter 1.1.

27.

Kigoshi, H.; Imamura, Y.; Sawada, A.; Niwa, H.; Yamada, K., Bull.
Chem. Soc. Jpn. 1991

, 64, 3735.

28.

Barton, D. H. R.; Crich, D.; Motherwell, W. B., J. Chem. Soc., Chem.
Commun. 1984

, 242.

29.

Barton, D. H. R.; Bridon, D.; Zard, S. Z., J. Chem. Soc., Chem. Commun.
1985, 1066.

30.

Feldman, K.; S. Simpson, R. E., J. Am. Chem. Soc. 1989, 111, 4878.

31.

Molander, G. A.; McKie, J. A., J. Org. Chem. 1992, 57, 3132.

32.

Kitching, W., Comprehensive Organic Synthesis 1991, 7, Chapter 4.2.

33.

Hill, C. L.; Whitesides, G. M., J. Am. Chem. Soc., 1974, 96, 870.

34.

Broka, C. A.; Lin, Y.-T., J. Org. Chem. 1988, 53, 5876.

35.

Pelter, A.; Smith, K., Comprehensive Organic Synthesis 1991, 7, Chapter
4.1.

36.

Brown, H. C.; Midland, M. M., Tetrahedron 1987, 43, 4059.

37.

Aoyama, Y.; Tanaka, Y.; Fujisawa, T.; Watanabe, T.; Toi, H.; Ogoshi, H.,
J. Org. Chem. 1987

, 52, 2555.

38.

Kabalka, G. W.; Reed, T. J.; Kunda, S. A., Synth. Commun. 1983, 13,
737.

39.

Takahashi, K.; Murakami, M.; Hagami, E.; Sasaki, H.; Kondo, Y.;
Mizusawa, S.; Nakamichi, H.; Iida, H.; Miura, S.; Kanno, I.; Uemura,
K.; Ido, T., J. Labelled Compd. Radiopharm. 1986, 23, 1111.

40.

Boyer, J. H., Chem. Rev. 1980, 80, 495.

41.

Riley, D. P.; Correa, P. E., J. Org. Chem. 1985, 50, 1563.

42.

Gangloff, A. R.; Judge, T. M.; Helquist, P., J. Org. Chem. 1990, 55, 3679.

43.

Chen, H. G.; Knochel, P., Tetrahedron Lett. 1988, 51, 6701.

44.

Gilchrist, T. L., Comprehensive Organic Synthesis 1991, 7, Chapter 6.1.

45.

Uemura, S., Comprehensive Organic Synthesis 1991, 7, Chapter 6.2.

46.

Ponsati, B.; Giralt, E.; Andreu, D., Tetrahedron 1990, 46, 8255.

47.

Posner, G. H., Org. React. 1975, 22, 253.

48.

Lambert, G. J.; Duffley, R. P.; Dalzell, H. C.; Razdan, R. K., J. Org.
Chem. 1982

, 47, 3350.

49.

Coleman, R. S.; Grant, E. B., Tetrahedron Lett. 1993, 34, 2225.

50.

Bolm, C.; Schlingloff, G.; Weickhardt, K., Tetrahedron Lett. 1993, 34,
3405.

51.

Rao, A. S., Comprehensive Organic Synthesis 1991, 7, Chapter 3.1.

52.

Sheldon, R. A.; Kochi, J. K. Metal-Catalysed Oxidations of Organic
Compounds

; Academic: New York, 1981.

53.

Chemla, F.; Normant, J., Tetrahedron Lett. 1995, 36, 3157.

54.

Klement, I.; Lutjens, H.; Knochel, P., Tetrahedron Lett. 1995, 36, 3161.

55.

Klement, I.; Lutjens, H.; Knochel, P., Tetrahedron 1997, 53, 9135.

56.

Klement, I.; Knochel, P., Synlett 1995, 1113.

57.

Sawamura, M.; Kawaguchi, Y.; Nakamura, E., Synlett 1997, 801.

58.

Moutel, S.; Prandi, J., Tetrahedron Lett. 1994, 35, 8163.

59.

Nakamura, E.; Inubushi, T.; Aoki, S.; Machii, D., J. Am. Chem. Soc.
1991, 113, 8980.

60.

Bernotas, R. C.; Ganem, B., Tetrahedron Lett. 1985, 26, 1123.

61.

Mayer, S.; Prandi, J., Tetrahedron Lett. 1996, 37, 3117.

62.

Nakamura, I.; Sato, K.; Imanishi, Y., Synlett 1995, 525.

63.

Klement, I.; Knochel, P., Synlett 1996, 1004.

64.

Cadot, C.; Dalko, P. I.; Cossy, J., Tetrahedron Lett. 2001, 42, 1661.

65.

Cadot, C.; Dalko, P. I.; Cossy, J.; Ollivier, C.; Chuard, R.; Renaud, P., J.
Org. Chem. 2002

, 67, 7193.

66.

Maeda, Y.; Nishimura, T.; Uemura, S., Bull. Chem. Soc. Jpn 2003, 76,
2399.

67.

Martiny, L.; Jorgensen, K. A., J. Chem. Soc., Perkin Trans. 1 1995, 699.

68.

Lin, Y.-M.; Miller, M. J., J. Org. Chem. 2001, 66, 8282.

69.

Khanna, V.; Maikap, G. C.; Iqbal, J., Tetrahedron Lett. 1996, 37, 3367.

70.

Patel, V. F.; Pattenden, G., J. Chem. Soc., Perkin Trans. 1 1990, 2703.

71.

Bamhaoud, T.; Prandi, J., Chem. Commun. 1996, 1229.

72.

Mayer, S.; Prandi, J.; Bomhaoud, T.; Bakkas, S., Tetrahedron 1998, 54,
8753.

73.

Desire, J.; Prandi, J., Eur. J. Org. Chem. 2000, 3075.

74.

Klement, I.; Henning, L.; Knochel, P., Angew. Chem., Int. Ed. Engl. 1997,
36

, 1454.

75.

Kaneda, K.; Ueno, S.; Imanaka, T., J. Chem. Soc., Chem. Commun. 1994,
797.

76.

Kaneda, K.; Ueno S.; Imanaka, T.; Shimotsuma, E.; Nishiyama, Y.; Ishii,
Y., J. Org. Chem. 1994, 59, 2915.

77.

Eade, S. J.; Adlington, R. M.; Cowley, A. R.; Walter, M. W.; Baldwin,
J. E., Org. Lett. 2005, 7, 3705.

78.

Liu, R.; Liang, X.; Dong, C.; Hu, X., J. Am. Chem. Soc. 2004, 126, 4112.

79.

Liu, R.; Dong, C.; Liang, X.; Wang, X.; Hu, X., J. Org. Chem, 2005, 70,
729.

80.

Einhorn, C.; Einhorn, J.; Marcadal, C.; Pierre, J.-L., Chem. Commun.
1997, 447.

81.

Kaneda, K.; Yamashita, T.; Matsushita, T.; Ebitani, K., J. Org. Chem.
1998, 63, 1750.

82.

Jiang, N.; Ragauskas, A. J., Org. Lett. 2005, 7, 3689.

83.

Trend, R. M.; Ramtohul, Y. K.; Ferreira, E. M.; Stoltz, B. M., Angew.
Chem., Int. Ed. 2003

, 42, 2892.

A list of General Abbreviations appears on the front Endpapers