Methyl Lithiodithioacetate1

[82452-67-3]  · C3H5LiS2  · Methyl Lithiodithioacetate  · (MW 112.16)

(enolate equivalent, capable of reacting as a carbon or sulfur nucleophile)

Preparative Methods: colorless solutions of the reagent are prepared by addition of Lithium Diisopropylamide to an ether or THF solution of methyl dithioacetate at -78 °C; reaction is complete in minutes.

Handling, Storage, and Precautions: solutions in THF are stable for at least 24 h at 20 °C.2 Solutions of the closely related ethyl lithiodithioacetate are reported to decompose rapidly above 0 °C.3

Reaction as a Carbon Nucleophile.

Methyl lithiodithioacetate gives aldol products with simple aldehydes.4 Selective conjugate addition is observed with enones (eq 1).5 The unexpected syn selectivity in the reaction arises from internal proton transfer to produce (1). Similar reactions conducted in the presence of Chlorotitanium Triisopropoxide (4 equiv) give exclusively the 1,2-addition product (eq 2).6 A variety of transformations possible for the products obtained from reactions with carbonyl compounds is described in a review article.1

Reaction as a Sulfur Nucleophile.

Methyl lithiodithioacetate reacts exclusively as a sulfur nucleophile with a variety of alkyl halides,7 epoxides,8 and with Chlorotrimethylsilane.9 Presumably, C-allylation products can be obtained by the thio-Claisen rearrangement, examined in detail with aldol products derived from methyl lithiodithioacetate.4

Related Reagents.

t-Butyl a-Lithioisobutyrate; Dilithioacetate; Ethyl Bromozincacetate; Ethyl Lithioacetate.

1. Metzner, P. S 1992, 1185.
2. Berrada, S.; Metzner, P.; Rakotonirina, R. BSF 1985, 881.
3. Meyers, A. I.; Walkup, R. D. T 1985, 41, 5089.
4. Beslin, P.; Perrio, S. T 1991, 47, 6275.
5. Berrada, S.; Desert, S.; Metzner, P. T 1988, 44, 3575.
6. Kpegba, K.; Metzner, P. TL 1990, 31, 1853.
7. Schuijl, P. J. W.; Brandsma, L.; Arens, J. F. RTC 1966, 85, 1263.
8. Guigné, A.; Metzner, P. PS 1985, 25, 97.
9. Sukhai, R. S.; Brandsma, L. S 1979, 455.

Michael Rathke & Robert Elghanian

Michigan State University, East Lansing, MI, USA

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