Diols from Grignard reactions

Cleavage of Si—C bonds (12,243-245). This oxidation can be used to convert vinylsilanes in three steps to syn- or anti-1,2-diols. Thus Grignard reagents cleave epoxides of vinylsilanes selectively to (3-hydroxy silanes, which can be oxidized with retention of configuration to 1,2-diols. When applied to an (E)-vinylsilane, the sequence results in the syn-l,2-diol the an -l,2-diol is obtained from a (Z)-vinylsilane by the same reactions. 

Diols, via Pinacol reaction, 10, 529 a-Diones, from Grignard reagents, 9, 55 DIOP, and chiral bisphosphane ligands, 10, 7 Diorganoditellurides halogenolysis, 9, 595... 

The unusual cyclopropane 551 was isolated [probably as the (5)-isomer] from Pistacia vera, together with the hydrated analog 552 551 was synthesized by Grignard reaction of cyclopropylmagnesium bromide with 4-methyl-3-cyclohexenone, and the diol 552 by lithium aluminum reduction of the epoxide of 551. ... 

A soln. of lj -methyl-5a-androstan-la,17 -diol in formic acid allowed to stand overnight at room temp. la-methyl-5a-androstan-ly9,17j -diol. Y 55%. - This epimerization appears to be a convenient prepn. of the la-methyl derivative, which could otherwise be obtained in only 3% yield from the Grignard reaction with the 1-ketoandrostane derivative. A. Romeo, V. Tortorella, and C. Vetuschi, Farmaco, Ed. Sci., 25, 227 (1968). 

Kavirayani R. Prassad s elegant brevicomin synthesis starts also from tartaric add, although actually from its Weinreb amide, which is converted into the desired intermediate hy a double Grignard reaction. Other key steps in the synthesis are the lead tetraacetate-mediated cleavage of the diol and the Wacker oxidation of the terminal alkene. [204]... 

The addition of Grignard reagents to aldehydes, ketones, and esters is the basis for the synthesis of a wide variety of alcohols, and several examples are given in Scheme 7.3. Primary alcohols can be made from formaldehyde (Entry 1) or, with addition of two carbons, from ethylene oxide (Entry 2). Secondary alcohols are obtained from aldehydes (Entries 3 to 6) or formate esters (Entry 7). Tertiary alcohols can be made from esters (Entries 8 and 9) or ketones (Entry 10). Lactones give diols (Entry 11). Aldehydes can be prepared from trialkyl orthoformate esters (Entries 12 and 13). Ketones can be made from nitriles (Entries 14 and 15), pyridine-2-thiol esters (Entry 16), N-methoxy-A-methyl carboxamides (Entries 17 and 18), or anhydrides (Entry 19). Carboxylic acids are available by reaction with C02 (Entries 20 to 22). Amines can be prepared from imines (Entry 23). Two-step procedures that involve formation and dehydration of alcohols provide routes to certain alkenes (Entries 24 and 25). 

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