Thiolysis imidates

Radical deoxygenation of an isolated tertiary hydroxy, desirable if involvement of adjacent stereocenters (in alkene formation or rearrangements) has to be avoided, presented problems in derivatization. Scheme 6 shows an inventive solution in which the alcohol (80) was converted to imidate (81). Choice of this electron-rich aromatic system secured smooth thiolysis to (82), which was efficiently deoxyge-... 

The most common source of imidates is nitriles (c/. Volume 6, Chapter 2.7) and, as these can be directly transformed into thioamides (c/. Section 2.4.3.4), this one-step approach is usually preferred. Moreover, depending on the reaction conditions and the substitution pattern, thiolysis of imidates may give thioesters rather than thioamides (c/. Volume 6, Chapter 2.5). However, some high-yield applications of imidates in thioamide synthesis have been reported and are detailed in equations (27) ° and (28). ... 

A similar concept for site-selective thiolysis of peptide bonds via backbone peptide bond activation can be found in Jensen s work (Fig. 18) [115]. The key step involves activation of the carboxy group of a Glu side chain by PyBrOP (19), resulting in the on-resin formation of the pyroglutamyl imide moiety. The activation renders the imide C-N bond susceptible to thiolysis, after which protected peptide thioesters were released from the solid support. 

Carbodi-imides can effect the 1,2- or 1,3-ring opening of amino-azirines, depending upon the nature of substituents, with the subsequent formation of zwitterions (129). These intermediates can be usefully converted into a variety of imidazolines by reduction, thiolysis, hydrolysis, and aminolysis (Scheme 8). 

Thiolysis and Thionation of Carboxylic Acid Derivatives. Thiolysis of imidates... 

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