[62762-48-5]  · C6H16S2Sn  · Bis(methylthio)(trimethylstannyl)methane  · (MW 271.00)

(precursor to acyl anion equivalent with 1,4-addition selectivity; dianion equivalent1)

Physical Data: bp (distillation) 93-95 °C/7 mmHg; n20D 1.5548.

Preparative Methods: commercially available bis(methylthio)methane is deprotonated by n-Butyllithium in THF/hexane at -60 to 0 °C. The resulting lithio derivative is quenched at -40 °C with 1 equiv of Chlorotrimethylstannane. An aqueous workup followed by vacuum distillation affords the bis(methylthio)(trimethylstannyl)methane reagent in 82% yield.2 The analogous Bis(methylthio)(trimethylsilyl)methane can be prepared by a similar procedure.3

Handling, Storage, and Precautions: organotin compounds should be considered toxic and should be handled with appropriate care. Use in a fume hood.


In contrast to lithiated 1,3-dithianes and related dithioacetals which undergo only 1,2-addition reactions with cyclic enones, lithiated bis(methylthio)(trimethylstannyl)methane furnishes 1,4-addition products in good yield. The reagent is metalated with Lithium Diisopropylamide in THF/HMPA at -78 to -30 °C; conjugate addition reactions (eq 1) are carried out from -78 to 25 °C. If the intermediate enolates are alkylated in situ with alkyl iodides, the products are predominantly the trans-2,3-disubstituted cycloalkanones (eq 2). The Bis(methylthio)(trimethylsilyl)methane reagent behaves similarly under these conjugate addition and alkylation reaction conditions.


The intermediate enolates can also be converted to dilithium derivatives by transmetalation (Methyllithium, THF, -100 °C) after removal of the diisopropylamine. The dilithium species can then be treated sequentially with electrophiles (eq 3). The dithioacetal anion is the more reactive nucleophile.

1. Seebach, D.; Bürstinghaus, R. AG(E) 1975, 14, 57.
2. Bürstinghaus, R.; Seebach, D. CB 1977, 110, 841 (CA 1977, 87, 6118n).
3. Seebach, D.; Kolb, M.; Gröbel, B.-T. CB 1973, 106, 2277 (CA 1974, 80, 27 320t).

Larry C. Blaszczak

Lilly Research Laboratories, Indianapolis, IN, USA

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