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In 2016, Maiti and coworkers reported the Pd‐catalyzed meta‐C–H olefination of synthetically versatile benzyl silanes using a nitrile‐based template (Scheme 2.60) [53]. Sequential olefinations through performing selective mono‐olefination and bis‐olefination were also demonstrated for synthesizing valuable 2,5‐ or 3,5‐hetero divinylbenzene derivatives. Notably, the templated could be easily installed, and meta‐olefinated toluene, benzaldehyde, and benzyl alcohols could be afforded while removing the silyl group with the template.

Scheme 2.60 meta‐C–H olefination of benzyl silanes.

Source: Modified from Patra et al. [53].

Subsequently in 2017, Maiti and coworkers also developed a pyrimidine‐based template assisted meta‐C–H cyanation of benzyl silanes using copper(I) cyanide as the cyanating agent (Scheme 2.61a) [41]. The meta‐cyano products are synthetically useful building blocks for preparing complex natural products as well as many drug molecules, and direct meta‐C–H cyanation of benzyl silane and converting the silyl group to hydroxy group could be applied to the preparation of antidepressant drug citalopram (Scheme 2.61b). It is worth mentioning that meta‐C–H allylation was also feasible with this template for benzyl silanes, although only limited examples were disclosed.

Scheme 2.61 (a) meta‐C–H cyanation of benzyl silanes. (b) Application of meta‐C–H cyanation of benzyl silanes.

Source: (a) Modified from Bag et al. [41].