[76373-10-9] · C4H11LiSn · (Trimethylstannylmethyl)lithium · (MW 184.80)
Solubility: sol ethers (THF, diethyl ether, DME).
Preparative Methods: treatment of bis(trimethylstannyl)methane with n-butyllithium or Methyllithium in dry THF.2 Bis(trimethylstannyl)methane can be obtained by the reaction of dichloromethane with 2 equiv of trimethylstannylsodium in liq NH3 (89%)3 or by the reaction of Diiodomethane with Tin(II) Bromide followed by the treatment with methylmagnesium iodide.4
Purification: the precursor bis(trimethylstannyl)methane should be distilled under reduced pressure before use (88-92 °C/15 mmHg).
Handling, Storage, and Precautions: since organotin reagents are toxic, all experiments should be performed in a good fume hood and with gloves.
The title reagent (1) or the analogous (tributylstannylmethyl)lithium react with ketones (2), affording b-stannyl alcohols (3) which undergo Peterson-type eliminations upon acid treatment or heating to methylene compounds (4) (eq 1).5
In contrast to the Wittig or Peterson reaction, which sometimes fails with enolizable ketones (5-20%),6 the present reaction gives the desired alkenes in good yields (64-96%).5 Remarkably, the reaction with cis-1-decalone in the presence of Hexamethylphosphoric Triamide proceeds with no epimerization, giving the cis-exo methylene compound in 91% yield, while the Wittig reaction affords the product as a mixture of cis and trans isomers in 32% yield.
Reagent (1) reacts with the oxiranes (5) to form g-stannyl alcohols (6) in the presence of 2 equiv HMPA. The alcohols (6) are easily converted into cyclopropanes (7) with Lewis acids (eq 2).5
The reaction pattern of (1) with carbonyl groups is influenced by the presence of leaving groups at the a-position. Acyclic a,b-epoxy ketones (8a) produce cyclopropanols (10) as a single product, while cyclic ketones (8b) produce mixtures of (10) and (12).7 Presumably nonselective attack of (1) produces the diastereomers of (9), which cyclize either to (10) or (11) under stereoelectronic control; b-elimination of (11) would produce (12). Cyclopropanols (10a) and (10b) can be converted into b,g-unsaturated ketones (13) and (14), respectively, upon Lewis acid treatment. Acyclic enone (13) (R = Me) can be obtained in one pot in about 80% yield from the epoxy ketones (8a) by successive treatments with reagent (1) and Hydrogen Chloride (eq 3).
Reagent (1) reacts with esters (15) to produce enolates (17), which are trapped by protons or aldehydes to afford methyl ketones or aldols, respectively (eq 4).
Enolates (17) react with methyl formate to afford b-keto aldehydes (20) in enol form. As an application, D-mycaroside (22) has been synthesized (eq 5).8
An analog of reagent (1), (trimethylstannyl)methylmagnesium iodide, has been used for methylenation of thioacetals (23) in the presence of a NiII catalyst (eq 6).9
Tadashi Sato & Jun Fujiwara
Waseda University, Tokyo, Japan