LITHIUM 1
permits the use of larger quantities of cosolvents for substrates
Lithium1
that are less soluble in NH3. The concentrations of Li in NH3
used in reactions vary widely, from 0.1 to 3 g Li/100 mL NH3.
Li
Concentrations near saturation form a second, less dense, bronze-
colored phase which is normally avoided.7
[7439-93-2] Li (MW 6.94)
Table 1 Solutions of alkali metals in liquid ammonia
InChI = 1/Li
InChIKey = WHXSMMKQMYFTQS-UHFFFAOYAN
ć%
Solubility6 at -33 C
(g metal/100 g NH3) Normal reduction potential5
ć%
(powerful reducing agent;1 used for partial reduction of aro-
Metal (g-atom M/mol NH3) at -50 C (V)
matics and conjugated polyenes;1e,m o conversion of alkynes to
Li 10.9 (0.26) -2.99
trans-alkenes;1a,h stereoselective reduction of hindered ketones;1l
Na 24.5 (0.18) -2.59
enone reduction and regioselective alkylation;1f,j reductive
K 47.8 (0.21) -2.73
cleavage of polar single bonds1a)
Reductions are performed either in the absence or presence
ć% ć%
Physical Data: mp 180.5 C; bp 1327 ą 10 C; d 0.534 g cm-3.
(Birch conditions1h) of a proton source, depending on the desired
7 6
Natural isotopic composition: Li (92.6 %); Li (7.4 %).
products.1a,i,4b An added proton source can effect reductions
ć%
Solubility: 10.9 g/100 g NH3 at -33 C (= 74.1 g/L NH3); 36.5
which do not occur in its absence (e.g. benzene reduction). It can
ć%
g/L MeNH2 at -23 C.
lead to higher saturation (e.g. in enone reduction) or suppress
Form Supplied in: under Ar, as solid in the form of wire, ribbon,
dimerization and base-catalyzed transformations of primary
rod, foil, shot, ingot, or as a powder; in mineral oil, as wire,
products. EtOH and t-BuOH are the most common proton donors.
shot, or as 25 30 wt % dispersions.
Primary alcohols protonate the intermediate anions more rapidly,
Purity: commercially available in up to 99.97% purity. In general,
but tertiary alcohols react more slowly with the metal. Other
lithium is not further purified except for cutting off the surface
proton donors are NH4Cl, H2O, and various amines.1a,e,4b
coating.
The order of adding the reagents can influence the product
Handling, Storage, and Precautions: best stored under mineral oil
distribution.1g Most often, Li is added last, until the blue color
in airtight steel drums and handled under Ar or He. Dispersions
of the solution persists. For less reactive substrates, alcohol
in mineral oil segregate on storage and uniformity is restored by
addition is delayed (Wilds Nelson modification).5b The reaction
stirring. The mineral oil is washed off under Ar with pentane or
is concluded by quenching excess Li mildly and efficiently with
hexane, and the metal is either dried in an Ar stream or rinsed
sodium benzoate8 or with excess EtOH and then NH4Cl, and
with the reaction solvent. Dry Li powder is extremely reactive
NH3 is allowed to evaporate.
towards air, H2O vapor, and N2. The metal reacts rapidly with
Distillation of NH3 from Na or through a BaO column removes
ć%
moist air at 25 C, but with dry air or dry O2 only at higher tem-
moisture and iron impurities. The latter catalyze the reaction of
ć%
peratures (>100 C). A slight blow can initiate violent burning.
alkali metals with the added alcohol and NH3.2 The Li NH3 ROH
ć%
Reaction with N2 already occurs at 25 C, but is inhibited by
system is less sensitive to traces of iron than Na NH3 ROH, which
traces of O2. Li reacts readily with H2O, but does not spon-
accounts in many instances for its superiority.9 Lithium Amide is
taneously ignite as the other alkali metals do. It reacts rapidly
less soluble in NH3 than Sodium Amide and Potassium Amide,
with dil HCl and H2SO4 and vigorously with HNO3. Ready
and base-catalyzed formation of side products is less frequent.1g,i
reaction occurs with halogens.
Nevertheless, in many cases similar results are obtained with Li
and Na in NH3; Li is preferred for less reactive substrates and Na
when overreduction is a problem.1
Lithium/Primary Amines Li forms stronger, but less selective,
Original Commentary
reducing agents with primary amines (Benkeser reduction).1d,h,k
Karin Briner
The higher reactivity is probably caused by higher reaction
Indiana University, Bloomington, IN, USA
temperatures1i,k and possibly also by smaller electron solvation.2
The reactivity can be modified by addition of alcohols.1h The
Reducing Systems. For reductions with Li, liquid Ammonia
Li amine solutions seem more sensitive to catalytic decompo-
or primary amines are most often the solvents of choice. Li dissoci- sition than Li in NH3.10 The choice of the amine is limited by
ates in these solvents more or less completely into Li+ and solvated
the solubility of Li; ethylamine and ethylenediamine are most
electrons, producing deep-blue metastable solutions.2 Ethereal
common. Na is hardly soluble in amines (e.g. more than 100
solvents (peroxide-free!) such as THF or DME may be used alone,
times less soluble in ethylenediamine at room temperature than
but are usually used as cosolvents with NH3 or amines. Li solu- Li).11 Reactions of calcium in amines have been described.12
tions in HMPA are quite unstable in contrast to Sodium solutions,
but are stabilized by THF.3 Reduction occurs by a sequence of sin- Reduction of Aromatic Compounds.1,13 Benzene and its
gle electron and proton transfers to the organic substrate, leading
derivatives are reduced to 1,4-cyclohexadienes with Li NH3 in
to saturation of multiple bonds or fission of single bonds.1a,i,4
the presence of a proton source (see also Sodium Ammonia).
Derivatives with electron-donating substituents lead to
Li NH3 Li has a higher normal reduction potential5 and molar
1-substituted cyclohexadienes. Thus reduction of anisole
solubility6 in liquid NH3 than Na or Potassium (see Table 1). This
derivatives furnishes 1-methoxycyclohexa-1,4-dienes (eq 1).9
Avoid Skin Contact with All Reagents
2 LITHIUM
Et Et CO2H
OH OH
1. Li NH3,  78 �C
HO2C CO2Me air
Li NH3
2. MeCH=CHCO2Me
(1)
70%
t-BuOH
87%
MeO MeO
CO2Me
(5)
Hydrolysis of such dienol ethers to cyclohex-3-enones or with
isomerization to cyclohex-2-enones has found wide application
Benzamides and alkyl benzoates can be reduced to the 1,4-
in syntheses of steroids, terpenoids, and alkaloids.1f,m Li is su-
dihydro amides and esters, respectively, with Li NH3 t-butanol,
perior to Na for the more difficult reductions of 1,2,3-substituted
but K NH3 t-butanol appears superior.13 However, Li may be
anisole derivatives,5b though sometimes even excess Li gives poor
results.14 Anisoles are more readily reduced than phenols (eq 2),15 better for in situ reductive alkylations, or K+ may be exchanged
with Li+ before the alkylation step.21 Reductive methylation of
but higher concentration of Li in NH3 may effect phenol reduction
N-benzoyl-L-prolinol derivatives afforded excellent diastereose-
to cyclohexenols (eq 3).16
lectivities, irrespective of the use of Li, Na, or K (eq 6).22
O O
OMe OMe
1. Li NH3, THF
N N
t-BuOH
(6)
1.5 M Li NH3
2. MeI
(2) R1 R1
t-BuOH
OMe OMe
73%
R1 = OMe, ca. 85%, de >260:1
R1 = Me, 90%, de <1:99
HO HO
The strongly activating and easily removable trimethylsilyl
group has been used to direct the regioselectivity of reduction
(eq 7).23
4.3 M Li NH3
(3)
EtOH
OMe OMe
HO HO
76% 1. Li NH3,  78 �C, 67%
(7)
2. NBu4F
50 60%
TMS
Electron-acceptor substituents enhance reduction rates and
promote 1,4-reduction at the substituted carbon atoms, irre-
The Li amine alcohol reagents also reduce benzene deriva-
spective of alkoxy, amino, or alkyl substituents. Benzoic acid
tives to cyclohexadienes, and are usually applied when reduc-
derivatives are readily reduced to the 1,4-dihydro derivatives. The
tion in NH3 fails.1h,k Thus reduction of dehydroabietic acid
presence of an alcohol is not necessary, in contrast to the deriva-
with Li NH3 t-BuOH afforded 35% of diene while Li EtNH2 t-
tives with electron-releasing substituents. It can even result in
C5H11OH gave 81% (eq 8).24 The importance of the nature
overreduction, as the lithium alcoholate facilitates isomerization
of the proton source is demonstrated by the fact that nei-
of the 1,4-dihydro product to the 3,4-dihydro isomer (eq 4).17
ther Li NH3 EtOH nor Li EtNH2 EtOH gave any appreciable
amount of reduction product.
CO2H
1. Li NH3
2. NH4Cl
Li EtNH2
CO2H (8)
t-C5H11OH
81%
(4)
CO2HCO2H
CO2H CO2H
1. Li NH3 Li NH3
Reduction with Li amine gives mainly cyclohexenes due to
2. EtOH EtOH
isomerization of the initially formed 1,4-diene by the strong
alkylamide base.1h,i Mixtures of regioisomers are formed, and
best results favoring the most stable isomer are obtained with
mixtures1h of primary and secondary amines (eq 9).25
The dienolate formed during the reduction can be alky-
+ isomers (9)
lated in situ with alkyl halides,18,19 epoxides,19 or ą,�-
OO
unsaturated esters (eq 5)20 to give 1-substituted dihydrobenzoic
Li EtNH2 79%, 87:13
acids. Rearomatization provides alkyl-substituted aromatic com-
Li EtNH2 Me2NH (1:1) 88%, 96:4
pounds.
A list of General Abbreviations appears on the front Endpapers
LITHIUM 3
Condensed aromatic hydrocarbons are reduced more easily steroids.37 This method is complementary to complex hydride
than those in the benzene series. Carefully chosen reaction condi- reductions, which mainly afford the axial alcohols. Bicyclo[2.2.1]
tions lead to the selective formation of different products.1b Most heptanones are reduced predominantly to the endo-alcohols.
extensive reductions are achieved with Li ethylenediamine,26 Similar results have been found with Na, K, and Ca.35
while Na NH3 is one of the mildest reagents.27 Birch and Slobbe
OH
discuss the reduction of heterocyclic aromatics.4b O
Lithium-induced cyclization of 1,1 -binaphthalenes followed
Li NH3
by oxidation of the dianion affords perylenes.28 3,10-Dimethyl-
(13)
EtOH
perylene was obtained in 95% (eq 10a).28a Cyclizations to tetra-
O
O
substituted perylenes proceeded in 36 40%,28b while similar
reactions with K seem somewhat higher yielding.29a However, 9ą:9� > 99:1
the synthesis of an 1-alkylated perylene was only successful with
Li (eq 10b).29b
ą,�-Unsaturated ketones are reduced to the ketone by
Li NH3.1j In fused ring enones the relative configuration at the
R1 R1
ring junction is determined by protonation at the �-carbon.38
Regioselective alkylation is achieved by trapping the intermediate
enolate with an alkyl halide,39a a strategy also applied to ene-
R2 R2
(10)
diones (eq 14).39b In the presence of a proton source, reduction
to the saturated alcohols occurs.40 Li EtND2 t-BuOD reduction
gives high yields of saturated ketones and has been used for
the stereoselective deuteriation at the �-carbon.41 Conversion
R1 R1
to alkenes is accomplished by phosphorylation of an enolate
(a) R1 = Me, R2 = H 1. Li, THF, "; 2. O2; 95%
formed by Li NH3 reduction and subsequent hydrogenolysis
(b) R1 = H, R2 = (CH2)5Me 1. Li, DME, "; 2. CdCl2; 30%
with Li EtNH2 t-BuOH (eq 15).42
1. K, DME, 25 �C; 2. CdCl2; <5%
O O
H
Reduction of Alkynes1b,h. Internal alkynes are reduced to 1. Li NH3
(14)
PhCH2
trans-alkenes with Li NH3 or stoichiometric amounts of Li in
2. PhCH2Br
H
amines. Excess Li in amines leads to alkanes. Li EtNH2 t-BuOH
65%
O O
efficiently reduced an alkyne precursor of sphingosine to the trans-
alkene with simultaneous N-debenzylation, while triple bond
1. Li NH3
reduction was incomplete with Na NH3 and Li NH3 (eq 11).30
O O
2. (EtO)2P(O)Cl Li EtNH2
O O
Li EtNH2
O O 56% t-BuOH
t-BuOH,  78 �C (EtO)2P(O)O
91%
O H
(11)
NBn NH
88%
OH C13H27 OH
C13H27
(15)
Dissolving metal reduction is the method of choice for the re-
H
duction of triple bonds in the presence of nonconjugated carboxyl
groups,31 where Lithium Aluminum Hydride4 in THF fails.
Reductions of aromatic ketones are complicated by pos-
Li NH3 afforded higher amounts of trans-alkenes in the reduction
sible pinacol formation, reduction of the aromatic ring, and
of some cyclic alkynes compared with Na NH3.32 Terminal triple
hydrogenolysis of the C O bond. Depending on the reaction con-
bonds are protected against reduction with Li NH3 by deproto-
ditions, 1-tetralone is reduced to tetralin or 1-tetralol (eq 16);43a
nation with alkali amide, but are completely reduced to double
bonds by Li (or Na) NH3 (NH4)2SO4 or by Li in amines.1c in fact, seven different products can be produced.43b
Suitably located carbonyl groups give rise to cyclization, yielding
1. Li NH3
vinylidenecycloalkanols,33 e.g. eq 12.33a However, the use of
O
K33a,34a or electrochemical reduction34b may give better results.
2. addition of
NH4Cl
Li NH3
96% (16)
O O OH
(NH4)2SO4
(12)
1. Li NH3
50% OH
O
2. NaOBz or
addition to
aq NH4Cl
Reduction of Ketones1a,b,l,35. Li NH3 EtOH reduces Aromatic aldehydes and ketones are alkylated and deoxy-
sterically hindered cyclic ketones to equatorial alcohols (eq 13)36 genated in a one-pot procedure using alkyl- or aryllithium,
and has been widely applied in the syntheses of 11ą-hydroxy followed by Li NH3 (eq 17).44
Avoid Skin Contact with All Reagents
4 LITHIUM
R2
O 1. R2Li
2. Li NH3
Li H2N(CH2)2NH2
R1 R1 (17)
(20)
3. NH4Cl
50 �C OH
65 97%
O 89%
R1 = H, alkyl, aryl
Li promoted reductions of allyloxy and benzyloxy esters54a and
esters of sterically hindered secondary and tertiary alcohols54b
Aliphatic Carboxylic Acids. Simple straight chain carboxylic
give rise to carboxylate cleavage, thus presenting a means of
acids are reduced by Li MeNH2 or Li NH3 to an intermediate
indirect deoxygenation of alcohols. Further reductive cleavages
imine which can either be hydrolyzed to the aldehyde or
have been found with activated cyclopropanes,55 N-oxides,56 and
catalytically reduced to the amine.45
sulfonamides.57
Li (and K) promoted reduction of TiCl3 in the McMurry reac-
Reductive Cleavage of Polar Single Bonds1a. Li in various
tion has been reported to be more reliable than the TiCl3/LiAlH4
solvents provides effective reagents for the cleavage of polar sin-
reagent.58
gle bonds. The cleavage tendency decreases in the order C I > C
Related Reagents. Calcium; Lithium Ethylamine; Potas-
Br > C Cl > C S > C O > C N > C C. Polyhalo compounds are
sium; Sodium; Sodium Alcohol; Sodium Ammonia.
completely reduced with Li and t-BuOH in THF (Winstein
procedure).46 Allylic, geminal, bridgehead, and vinylic halogen
atoms are removed, the latter stereospecifically. NH3 and amines
have been avoided as solvents due to potential reaction with
First Update
the alkyl halides by elimination or substitution.1a,47a However,
Brian M. Mathes
Li NH3 systems successfully reduce vinylic, bridgehead, and
Eli Lilly and Company, Indianapolis, IN, USA
cyclopropyl halides47b,c and sometimes give better results than
the Winstein Gassman procedures (eq 18).47c
Reduction of Nitrones to Amines. Reduction of nitrones has
been accomplished under mild conditions using a NiCl2/Li sys-
MeO OMe
MeO OMe
tem with a catalytic amount of 4,4 -di-tert-butylbiphenyl (DTBB)
Cl
Li NH3 EtOH
Cl
(eq 21).59 This system has been shown to be general for aliphatic
(18)
Et2O,  78 �C
and benzylic nitrones. In the absence of NiCl2 the reaction pro-
85%
Cl Cl
ceeds to give the deoxygenated imine (eq 22). This same method-
HOCH2 NH2 HOCH2 NH2
ology has been extended to the reductions of hydrazines, azo,
azoxy, and amine N-oxides.60
Alkyllithium reagents nowadays often replace Li for the prepa-
Li, NiCl2 2 H2O, DTBB, THF
ration of organolithium compounds from alkyl or aryl bromides.48
(21)
71%
Li has been used to couple alkyl and aryl halides in Wurtz or
N+ N
Wurtz Fittig-type reactions,49 though the use of Na is much more
H
O
important. Reduction of monosubstituted alkyl halides or selec-
tive reduction of geminal dihalides are best carried out with metal
Li, DTBB, THF
(22)
or complex hydrides or by catalytic hydrogenation.1b
67%
Sulfides, sulfoxides, and sulfones are reductively cleaved with
N+ N
lithium.50 Reduction of sulfides in THF is improved with catalytic
O
naphthalene. Li EtNH2 gave better results than Sodium Amalgam
for the cleavage of the C S bond in sulfones (eq 19),51a,b and than
Raney Nickel for some sulfide cleavage.51c Selenides are cleaved Conversion of Lactones to Acetylenic Alcohols. The con-
similarly.52 Thio- and selenoacetals are reduced to alkanes. version of lactones to acetylenic alcohols was realized by
the reductive elimination of a dichloromethylene intermediate
SO2Ph (eq 23).61The great number of lactones naturally available in the
chiral pool allow this methodology to be a productive source of
chiral starting materials.
Li EtNH2
(19)
 75 �C
90%
1. CCl4, PPh3
O
O
(Z):(E) = 90:10 2. Li, THF
82%
Allyl, benzyl, and aryl ethers are cleaved by Li in NH3
or amines.1a,b Sterically hindered steroid epoxides, which are
not cleaved with LiAlH4, are converted into axial alcohols by
(23)
Li EtNH2.1b Li ethylenediamine efficiently cleaves sterically
OH
hindered epoxides to tertiary alcohols (eq 20).53
A list of General Abbreviations appears on the front Endpapers
LITHIUM 5
Reductive Alkylation of Arenes. Lithium arene dianions from unwanted addition to the carbonyl group. Primary alkyl chlorides
polycyclic aromatic hydrocarbons such as naphthalene and an- have exhibited the best yields, but the less explored aromatic and
thracene react with n-alkyl fluorides to obtain regiochemically unsaturated compounds are also discussed. Unfortunately, ą,� un-
controlled alkylated dihydroarenes by simple treatment of arenes saturated carboxylates give product in low yield (10 30%) due to
with lithium in THP (eq 24).62 The system undergoes alkylation multiple additions.
via an SN2 transition state instead of simple radical coupling.
O
In all cases, the experimental observations were consistent with
MO calculations performed on this system. The lack of regioi-
Li, DTBB, MeI, THF
someric contaminants adds more evidence that this reaction does
74%
not progress through a radical intermediate.
R
CH3
1. Li, THP
(26)
2. RF
OO
Li, CH3Cl, THF
OLi
(27)
100%
1. Li, NH3
(24)
2. RX
R
Formation of Primary Amines. Primary amine synthesis
through modified Barbier-type reactions have been described.66
Conversion of an aromatic or aliphatic aldehyde with LiHMDS
to the intermediate imine followed by treatment with benzyl bro-
Reduction of Aromatic Ketones and Alcohols. Use of the
mide in the presence of lithium metal affords the primary amines
electron-transfer reagent DTBB under ultrasonic irradiation con-
(eq 28). Addition of organolithium or Grignard reagents to imines
ditions provides a very simple extension of common Li-NH3 re-
have been used in the past to afford such amines, however, the
duction methodologies of alcohols and ketones.43 Lithium is the
low electrophilicity of the imine can hinder this transformation.
preferred partner with DTBB and ultrasound (eq 25) since sodium
Sonication appears to both influence the reaction time and yield.
is not tolerated at all and reactions with potassium proceed at a
Without sonication, the reactions undergo more side-reactions
much slower rate.63 Unfortunately, attempts to reduce aliphatic
(Wurtz couplings) and decomposition of the imine starting
ketones using this method have failed. This method can also be
material.
extended to the reductive alkylation of the ketone by addition of
alkyl halides before reaction quench (eq 26).63 O
1. LHMDS, ether
H
Br
2. Li, ether ,
N
OH
Li, DTBB, THF
41%
H NH2
(28)
N
Reductive Cleavage of Polar Bonds. The use of lithium for
(25)
the cleavage of polar bonds has been described above. However,
recent literature provides for a tandem cleavage/alkylation
methodology.67 Scission of methoxy ethers with lithium in THF
Synthesis of Ketones.64,65 A wide range of ketones can be generates a carbanion that can be trapped with an alkyl halide. In
directly accessed from lithium carboxylates in the presence the case of a dimethoxy species, this reaction can occur twice in
of alkyl chlorides and excess lithium metal with sonication good yield (eq 29). The expected Wittig side-product was avoided
ć%
(eq 27).64,65 This method obviates the need for conversion to acid by lowering the temperature to -40 C. This transformation
chlorides or amides commonly employed for this conversion. It allows the dialkylation of aromatic aldehydes which has been
is imperative that the lithium carboxylate is used as this prevents previously unreported.
Avoid Skin Contact with All Reagents
6 LITHIUM
OMe
23. Rabideau, P. W.; Karrick, G. L., Tetrahedron Lett. 1987, 28, 2481.
1. Li, THF, C4H9Br
24. Burgstahler, A. W.; Worden, L. R., J. Am. Chem. Soc. 1964, 86, 96.
OMe
2. Li, THF, C4H9Br
25. Borowitz, I. J.; Gonis, G., Kelsey, R., Rapp, R.; Williams, G. J., J. Org.
86%
Chem. 1966, 31, 3032.
26. Reggel, L.; Friedel, R. A.; Wender, I., J. Org. Chem. 1957, 22, 891.
27. Rabideau, P. W.; Burkholder, E. G., J. Org. Chem. 1978, 43, 4283.
28. (a) Jaworek, W.; V�gtle, F., Chem. Ber. 1991, 124, 347 (Chem. Abstr.
(29)
1991, 114, 101 319p). (b) Michel, P.; Moradpour, A., Synthesis 1988,
894.
29. (a) Koch, K.-H.; M�llen, K., Chem. Ber. 1991, 124, 2091. (b) Anton,
U.; G�ltner, C.; M�llen, K., Chem. Ber. 1992, 125, 2325.
30. Julina, R.; Herzig, T.; Bernet, B.; Vasella, A., Helv. Chim. Acta 1986,
69, 368.
31. Dear, R. E. A.; Pattison, F. L. M., J. Am. Chem. Soc. 1963, 85, 622.
1. (a) Smith, M., In Reduction: Techniques and Applications in Organic
32. Svoboda, M.; Z�vada, J.; Sicher, J., Collect. Czech Chem. Commun.
Synthesis; Augustine, R. L., Ed.; Dekker: New York, 1968; Chapter 2.
1965, 30, 413.
(b) Hudlickó, M., Reductions in Organic Chemistry; Horwood:
33. (a) Stork, G.; Malhotra, S.; Thompson, H.; Uchibayashi, M., J. Am.
Chichester, 1984. (c) Birch, A. J., Q. Rev., Chem. Soc. 1950, 4, 69.
Chem. Soc. 1965, 87, 1148. (b) Miller, B. R., Synth. Commun. 1972, 2,
(d) Benkeser, R. A., Adv. Chem. Ser. 1957, 23, 58. (e) Birch, A. J.; Smith,
273.
H., Q. Rev., Chem. Soc. 1958, 12, 17. (f) Steroid Reactions; Djerassi,
34. (a) Stork, G.; Boeckmann, R. K., Jr.; Taber, D. F., Still, W. C., Singh,
C., Ed.; Holden-Day: San Francisco, 1963. (g) Harvey, R. G., Synthesis
J., J. Am. Chem. Soc. 1979, 101, 7107. (b) Swartz, J. E.; Mahachi, T. J.;
1970, 161. (h) Kaiser, E. M., Synthesis 1972, 391. (i) Birch, A. J.; Subba
Kariv-Miller, E., J. Am. Chem. Soc. 1988, 110, 3622.
Rao, G. S. R., Adv. Org. Chem. 1972, 8, 1. (j) Caine, D., Org. React.
1976, 23, 1. (k) Brendel, G., Lithium Metal in Organic Synthesis; In 3rd 35. Huffman, J. W., Comprehensive Organic Synthesis 1991, 8, 107.
Lect.-Hydride Symp.; Metallges. AG: Frankfurt/Main, 1979; p 135. (1)
36. Huffman, J. W.; Desai, R. C.; LaPrade, J. E., J. Org. Chem. 1983, 48,
Huffman, J. W., Acc. Chem. Res. 1983, 16, 399. (m) Hook, J. M.; Mander,
1474.
L. N., Nat. Prod. Rep. 1986, 3, 35. (n) Rabideau, P. W., Tetrahedron 1989,
37. Giroud, A. M., Rassat, A., Bull. Soc. Chem. Fr. 1976, 1881 (Chem.
45, 1579. (o) Rabideau, P. W. Marcinow, Z., Org. React. 1992, 42, 1.
Abstr. 1977, 87, 6251a).
2. (a) Dye, J. L., Prog. Inorg. Chem. 1984, 32, 327. (b) Thompson, J. C.,
38. Toromanoff, E., Bull. Soc. Chem. Fr. 1987, 893 (Chem. Abstr. 1988,
Monographs on the Physics and Chemistry of Materials: Electrons in
109, 128 193b).
Liquid Ammonia; Oxford University Press: Fair Lawn, N. J.; 1976.
39. (a) Stork, G.; Rosen, P.; Goldman, N.; Coombs, R. V.; Tsuji, J., J. Am.
3. Gremmo, N.; Randles, J. E. B., J. Chem. Soc., Faraday Trans. 1 1974,
Chem. Soc. 1965, 87, 275. (b) Stork, G.; Logusch, E. W., J. Am. Chem.
70, 1480.
Soc. 1980, 102, 1218.
4. (a) Dewald, R. R., J. Prakt. Chem. 1975, 79, 3044. (b) Birch, A. J.,
40. Samson, M.; De Clercq, P.; Vandewalle, M., Tetrahedron 1977, 33, 249.
Slobbe, J., Heterocycles 1976, 5, 905.
41. (a) Burgstahler, A. W.; Sanders, M. E., Synthesis 1980, 400. (b) See
5. (a) Pleskov, V. A., J. Phys. Chem. (U.S.S.R) 1937, 9, 12 (Chem. Abstr.
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