Thiols, tertiary reductive decarboxylation

The free radical chain reaction of 0-acyl thiohydroxamates with a tertiary thiol (r-butyl, triethylmethyl or more recently t-dodecyl) is by far the most wide-ranging reductive decarboxylation method describe to date7 A wide variety of functional groups, including aldehydes, ketones, esters, amides, isolated and conjugated double bonds, are tolerated. Representative examples are given in equations (10) and (11). ... 

Hydrogen atom donors such as non-nucleophilic tertiary thiols or tri-n-butyltin hydride are extremely efficient traps for the capture of the alkyl radical R derived from O-acyl thiohydroxamates, thus providing a very efficient method for reductive decarboxylation (Scheme 3). In practical terms, the use of the mercaptan is preferred since the tertiary alkyl pyridyl disulfide can be easily removed during work up by a simple acid extraction. The reaction has been successfully applied to a very wide range of complex substrates [8] possessing primary, secondary, or tertiary aliphatic carboxylic acids, and reactions at room temperature or below require only photolysis from a simple tungsten lamp and often involve in situ O-acyl thiohy-droxamate derivatization. 

Thus, as shown by the example in Scheme 42, sequential treatment of the trime-thylsilyl ethers of a variety of tertiary alcohols with oxalyl chloride and the parent thionohydroxamic acid furnishes mixed oxalate esters which undergo reductive deoxygenation on subsequent reaction with a tertiary thiol in refluxing benzene [46]. The selectivity of this method for tertiary alcohols arises as a consequence of the relativity slow rates of decarboxylation of primary and secondary alkoxycarbonyl radicals. 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ ]

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