Carbamoyl migration

LDA metalation of the 2-carbamate 344 followed by aldehyde quench afforded mixtures of products 347 and 348 (Scheme 106). The formation of the carbostyryl derivative 348 can be rationalized by an intramolecular carbamoyl migration (349- 350) (Scheme 107) driven by the leaving group ability of the 2-carbamoyl group. 

The similarly and equally accessible biaryl O-carbamate 142 (Scheme 38) requires ortho substitution (PG = OMe) or protection (PG = SiEts) to avoid anionic ortho Fries rearrangement (141) and to launch a DreM pathway leading to 144 using LDA under vigorous conditions [65]. For PG = TMS, carbamoyl migration to the incipient a-silylmethyl anion occurs... 

An unprecedented O C 1,3-carbamoyl migration of the ortto-lithiated species 252 in the course of a directed metalation reaction of carbamates 251 to give the sahcy-lamides 253 was first reported by Sibi and Snieckus (equation 116) . This approach was afterwards developed in a series of investigations . ... 

Direct ortho lithiation of O-aryl carbamates and 0 to C carbamoyl migration to give salicylamides. 

Other potentially useful reactions, similarly unexplored, involve the lateral met-allation cyclization to oxindoles, 86 —> 88, the N-to-ortho-C carbamoyl migration to anthranilamides, 86 —> 89, and the thereby facilitated further DoM chemistry to produce 90, substances that may further be used in cross-coupling reactions, for example, E = hal, B(OR)2 [133], This anionic arene chemistry has complementarity to the Friedel-Crafts reactions (for 85 and 87) and synthetic consequences for a variety of heterocyclic frameworks represented in the structures in Scheme 14.21. 

James, C.A. (1998) The directed remote metalation - Carbamoyl migration reaction. Total syntheses of the defucogilvocarcins and amottin 1 and synthesis of heteroarylfused benzopy-ranones. Ph.D. Thesis. University of Waterloo, Canada. 

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