Migration carbamoyl groups

Lithiated alkyl carbamates [e.g. 44 from 32a (Cb for Cby)] decompose above —40°C with migration of the carbamoyl group to produce a-hydroxy carboxamides 45 (equation 8) . ... 

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. 

Treatment of metal-free BLM with triethylamine in aqueous alcohol at room temperature induces migration of the carbamoyl group at 3-0-position of the mannose to 2-0-position to give iso-BLM [32]. Treatment of copper complex of BLM under the same condition causes epimerization at the a-position of the pyrimidine ring to afford pi-BLM (Fig. 6) [33]. /so-BLM and epi-BLM exhibited remarkably lowered antimicrobial activity [32, 33]. 

Curtius-type behaviour is followed on irradiation of the azide 610 at 10 K when methoxyisocyanate is obtained by migration of the methoxy group from carbon to nitrogen" . Carbamoyl azide is also photolabile under similar conditions and provides a route to aminonitrene The substituted amide derivative 611 also undergoes conversion to the corresponding isocyanate and, if this is brought about in the presence of carbodiimides, cycloaddition results in the formation of triazoles. ... 

Under similar conditions, migration of the vinyl fragment does not occur in 2-(l-hydroxy-2-carbamoyl-2-cyanovinyl)-l-methylpyrroles. The most probable cause is a strong intramolecular hydrogen bond between the hydroxyl proton and carbonyl group (x-ray diffraction (XRD) data), considerably lowering the acidity of the hydroxyl (-3.3 un. pX ) [568]. 

---