LEAD(II) ACETATE 1
Lead(II) Acetate Conversion of Isocyanides into Isothiocyanates.3 Reactions
of isocyanides with dibenzoyl disulfide occur smoothly in the pres-
ence of this reagent to give isothiocyanates in high yield (eq 2).
Pb(OAc)2·3H2O
The activity of this reagent is almost identical with that of Thal-
lium(I) Acetate. In this reaction, a complex of the reagent with
[301-04-2] C4H12O7Pb (MW 379.33)
dibenzoyl disulfide is believed to be the key intermediate in the
InChI = 1/2C2H4O2.3H2O.Pb/c2*1-2(3)4;;;;/h2*1H3,(H,3,4);
sulfurization of the isocyanide (eq 3).
3*1H2;/q;;;;;+2/p-2/f2C2H3O2.3H2O.Pb/q2*-1;;;;m
InChIKey = MCEUZMYFCCOOQO-TXGYFSJOCT O
NC
NCS
Pb(OAc)2
S Ph
+ (2)
Ph S
(desulfurization reagent2,3)
89%
O
ć% ć%
Physical Data: mp 75 C when rapidly heated; above 100 Cit
begins to lose acetic acid and decomposes completely above
Pb(OAc)2
O
ć%
O
200 C; d 2.55 g cm-3.
Pb(OAc)2
S Ph
ć% S Ph
Solubility: 0.456 g mL-1 in H2Oat 15 C; 2.0 g mL-1 in H2O Ph S
Ph S
ć%
at 100 C; 0.033 g mL-1 in ethanol; slightly sol diethyl ether; O
O
+
freely sol glycerol. 
C N
Form Supplied in: colorless crystals or white granules or powder;
slowly effloresces; widely available; may contain insoluble lead
O
 S Ph
(AcO)2Pb
carbonate resulting from exposure to air.
C+
N S Ph
O  Pb(OAc)2
Drying: dry at rt because of facile dehydration. Drying over
 (PhCO)2S
H2SO4 at rt leads to formation of the anhydride.
NCS
Purification: recrystallize from water containing 2 3% acetic
(3)
acid.
Handling, Storage, and Precautions: poisonous; carcinogen;
LD50 200 mg kg-1 (intraperitoneal in rats); avoid breathing
dust and handle only in a fume hood. Keep tightly closed for
Elimination of H2S.4 This reagent is used for the conver-
storage; readily converts to complex salts. Incompatible with
sion of thioureas to cyanamides by elimination of H2S under mild
acids, alkalies, sulfates, sulfites, citrates, tartrates, chlorides,
conditions, as illustrated in eq 4.
carbonates, tannin, phosphates, resorcinol, salicylic acid, and
phenol.
S
N
HN NH2 Pb(OAc)2, KOH HN
Cl
Cl (4)
Neutralization of HCl.1 In the synthesis of Ä…-aminodiethyl-
 PbS
acetic acid via acid hydrolysis of the cyanohydrin of diethyl
72 74%
ketone, the crude amino acid hydrochloride is neutralized by lead
hydroxide (prepared by hydrolysis of this reagent with sodium
hydroxide) to yield the amino acid in liberated form (eq 1). This
procedure appears to be superior to that using Lead(IV) Oxide for Acetoxylation of Allylic Bromide.5 This reagent is used for
this neutralization. the preferential replacement of a bromine atom by an acetoxy
group in 1-chloro-3-bromocycloalkenes (eq 5). Lead(II) acetate
is superior to Silver(I) Acetate for this transformation.
O
NC OH
NaCN, NH4Cl NH3
Cl
Et Et Et Et Cl
+
Pb(OAc)2
NC NH2 HO2C NH3 Cl HO2C NH2
(5)
(CH2)n (CH2)n
Pb(OAc)2
 PbBr2
HCl
Et Et Et Et Et Et (1)
80 90%
NaOH Br OAc
39 43%
n = 6 9
Removal of Selenium and Selenious Acid.2 Selenium(IV)
Preparation of Cyclic Disulfides.6 Reactions of dithiols with
Oxide and selenious acid are good reagents for the oxidation
an aqueous solution of this reagent give lead dithiolates in nearly
of the Ä…-methylene carbon of carbonyl compounds to give 1,2-
quantitative yield. The dithiolates react with sulfur in benzene at
dicarbonyl compounds. However, it is difficult to remove the
rt to give the cyclic disulfides in high yields without the formation
resulting colloidal selenium and excess of the oxidant from the
of polymeric disulfides (eq 6).
desired product in this method. A procedure for the oxidation of
paraldehyde to glyoxal and the isolation of the product as the
bis-bisulfite addition compound specifies the use of lead(II)
SH S S
Pb(OAc)2
S
(CH2)n (CH2)n (CH2)n (6)
Pb
acetate. Thus the addition of aqueous solution of this reagent to
PhH
SH S S
the reaction mixture gives insoluble lead selenite as a precipitate
n = 3 6 82 92%
which is removed readily by filtration.
Avoid Skin Contact with All Reagents
2 LEAD(II) ACETATE
1. Steiger, R. E., Org. Synth., Coll. Vol. 1955, 3, 66. 6. Cragg, R. H.; Weston, A. F., Tetrahedron Lett. 1973, 655.
2. Ronzio, A. R.; Waugh, T. D., Org. Synth., Coll. Vol. 1955, 3, 438.
3. Tanaka, S.; Uemura, S.; Okano, M., Bull. Chem. Soc. Jpn. 1977, 50, Tatsuo Oida
2785.
Kyoto Institute of Technology, Kyoto, Japan
4. Kurzer, F., Org. Synth., Coll. Vol. 1963, 4, 172.
Sakae Uemura
5. Schank, K.; Eistert, B.; Felzmann, J. H., Chem. Ber. 1966, 99, 1414.
Kyoto University, Kyoto, Japan
A list of General Abbreviations appears on the front Endpapers