Thiophilic reactions of aryllithium bearing a bulky bowl-type substituent with carbon disulfide

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Phosphorus, Sulfur, and Silicon
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Thiophilic Reactions of
Aryllithium Bearing a Bulky
Bowl-Type Substituent With
Carbon Disulfide
Kaori Mogi a a , Keiko Takenaka a & Renji Okazaki a
a Department of Chemical and Biological Science ,
Faculty of Science, Japan Women's University ,
Tokyo, Japan
Published online: 16 Aug 2006.
To cite this article: Kaori Mogi , Keiko Takenaka & Renji Okazaki (2005) Thiophilic
Reactions of Aryllithium Bearing a Bulky Bowl-Type Substituent With Carbon Disulfide,
Phosphorus, Sulfur, and Silicon and the Related Elements, 180:5-6, 1501-1502, DOI:
10.1080/10426500590913384
To link to this article: http://dx.doi.org/10.1080/10426500590913384
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Phosphorus, Sulfur, and Silicon, 180:1501–1502, 2005
Copyright © Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500590913384
Thiophilic Reactions of Aryllithium Bearing a Bulky
Bowl-Type Substituent With Carbon Disulfide
Kaori Mogi
Keiko Takenaka
Renji Okazaki
Department of Chemical and Biological Science, Faculty of Science,
Japan Women’s University, Tokyo, Japan
Reactions of aryllithium that have a bulky bowl-type substituent,
Bmt (Bmt = 4-t-butyl-2,6-bis[2,2ꢀꢀ,6,6ꢀꢀ-tetramathyl]phenyl) with car-
bon disulfide, afforded various compounds via interesting anion in-
termediate 1, resulting from a thiophilic attack of the lithium
reagent.
BmtLi reacted with carbon disulfide to give alkene cis-3 (R CH3)
after treatment with methyl iodide. cis-3 (R CH3) isomerized to ther-
modynamically more stable trans-3 (R CH3) upon heating or treat-
ment with acid. The formation of cis-3 (R CH3) can be explained in
terms of reaction of dianion 2, which is formed by dimerization of anion
1, which has dithiocarbene-type canonical structure 1b, with methyl
iodide. The use of p-methylbenzyl bromide instead of methyl iodide
gave trans-3 (R CH2C6H4CH3-p). We also examined more bulky alkyl
halides, MesCH2Br and TipCH2Br (Tip = 2,4,6-tri-isopropylphenyl).
These alkyl halides did not react with 2 but with monomeric anion 1a
to afford the corresponding dithioester 4. This suggests the existence
of a monomer 1–dimer 2 equilibrium. Reaction with a sterically more
congested alkyl halide, Mes∗CH2Br (Mes∗ = 2,4,6-tri-t-butylphenyl), re-
sulted in the formation of 5. This clearly shows the elimination of carbon
monosulfide from 1. This elimination occurs most likely because Mes∗
group is so sterically congested that even 1 could not react with this bro-
mide at low temperature. The even more bulky alkyl halide, TmtCH2Br
(Tmt = 2,2ꢀꢀ,6,6ꢀꢀ-tetramathyl-m-terphenyl) did not react with 6, and
only thiol BmtSH was obtained. Interestingly, use of protic acid such
as trifluoromethanesulfonic acid and aq. HCl as a quenching reagent
Received July 9, 2004; accepted October 5, 2004.
Address correspondence to Kaori Mogi, Department of Chemical and Biological Sci-
ence, Faculty of Science, Japan Women’s University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo
112-8681, Japan. E-mail: kaori.mogi03@gr.jwu.ac.jp
1501

1502
K. Mogi et al.
resulted in unexpected formation of dithioformate 7. The mechanism
for the formation of these products is discussed.
Structures of 3, 4, 5 and 7 were established by X-ray crystallographic
analysis.