Butyl 2- p-Tolylsulfinyl acetate

Preparative Methods conveniently prepared - by reaction of the magnesium enolate of r-butyl acetate (readily made with Bromomagnesium Diisopropylamide) with (-)-(lR,2S,5R)-Menthyl (S)-p-Toluenesulfinate (eq 1). It was also made in 91% yield by reacting a solution of Lithium Diisopropylamide with (R)-(+)-methyl p-tolyl sulfoxide and 7-butyl carbonate (eq 2). It should be noted that asymmetric oxidation of 7-butyl 2- p-tolylsulfinyl)acetate with a modified Sharpless reagent gave a 

Aldol-Type Addition. Aldol-type addition of the magnesium enolate of (R)-(+)-7-butyl 2-(p-tolylsulfinyl)acetate, prepared with 7-butylmagnesium bromide, with aldehydes and ketones afforded, after desulfurization with Aluminum Amalgam, p-hydroxy esters in very high diastereoselectivity (eq Two chiral centers are created in the first step with very high diastereoselectivity (mainly one diastereomer is formed). A model M based on the structure of the sulfinyl ester enolate (determined by C NMR) and on electrophilic assistance of magnesium to the carbonyl approach, was proposed to explain and predict the absolute configuration of the two created chiral centers.  

The first application of this aldol-type asymmetric synthesis was reported by Corey during the later stages of the total synthesis of maytansine. This result (eq 4) showed that the 7-butyl ester could be replaced by a phenyl ester as long as the same base, 7-BuMgBr, is used for the condensation. The reaction of the a,p-unsaturated aldehyde gave, after desulfurization, the corresponding p-hydroxy ester in 80% yield and 86% de. 

Optically active five- and six-membered lactones were also prepared by this aldol-type addition (eq 5).  

Propargylic aldehyde was also used to prepare, by condensation with (+)-(R)-7-butyl p-tolylsulfinylacetate, a precursor of the C-3-C-8 fragment of leukotriene B4 (eq 6).  

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Preparative Methods the synthesis of this compound was first reported by methylation of (R)-(+)-t-Butyl 2-(p-Tolylsulfinyl)acetate via enolate generation with lithium bases such as n-Butyllithium or t-Butyllithium at 0 °C and with only lodomethane as the alkylating agent (eq 1). The diastereomeric ratio was shown by H NMR to be 50 50 with BuLi and 42 58 with t-BuLi. The title compound was also prepared from (-)-(1R,2S,5R)-Menthyl (S)-p-Toluenesulfinate and the magnesium enolate of t-butyl propionate in 68% yield as a 1 1 ratio of the two possible diastereomers (eq 2). ... 

R)-( -I- )-r-Butyl(p-tolylsulfinyl)acetate, 106 r-Butyl 2-(p-tolylsulfinyl)pn>pionate, 538... 

Related Reagents. (R)-(+)-r-Butyl 2-(p-Tolylsulfinyl)-propionate (R)-(+)-Methyl p-Tolyl Sulfoxide (R)-(+)-Phenyl (p-Toluenesulfinyl)acetate. 

Similarly, the magnesium enolate of /-butyl () )-(p-tolylsulfinyl)acetate adds to aldehydes and ketones. The subsequent reductive desulfurization yields Ae corresponding optically active P-hydroxy esters (Scheme 27). 2 This process can be utiliz for preparation of a synthetic intermediate (95) of maytan-sine with a selectivity of 93 7 (equation 23). Michael-type addition of /-butyl (/ )-(p-tolylsulfinyl)ace-tate to crotonic ester with NaH in DMF has also been reported, but the enantiomeric excess of the desulfurized product is very low (12%). ... 

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