Xylene Overman rearrangement

The synthesis of a fully functionalized cyclopentane core structure of pactamycin, a potent antitumor antibiotic, involves Overman rearrangement as a key reaction. Heating a mixture of potassium carbonate and the imidate derived from allylic alcohol 68 in p-xylene yields the desired trichloroacetamide 69 as a single isomer in 90% yield from 68. In this reaction, potassium carbonate is a crucial additive as no desired product is obtained when the same reaction is carried out without potassium carbonate. Trichloroacetimidate 69 has been elaborated into the tricyclic compound 70 which contains all the carbon atoms for the core cyclopentane of pactamycin,... 

The Overman rearrangement of the disubstituted allylic trichloroace-timidates has also been used in the construction of trisubstituted carbons bearing a nitrogen substituent. For instance, heating a solution of the imidate 71 in refluxing xylene fiimishes the allylic trichloroacetamide 72 in good yield. Compound 72 is a precursor to aminocyclopentanol Ti ... 

Overman rearrangement of the diacetoneglucose derived allylic trichloroacetimidate 70 by heating in xylene gives the branched-chain compound 71/ Oxidative cleavage of the double bond with concomitant loss of the trichloroacetimidate affords access to D-amino acids. 

The Overman rearrangement converts allylic trichloroacetimidates into trichlo-roacetamides in presence of o-xylene under microwave irradiation (Gajdosikova et al., 2008). The reaction time was shorter as compared to the conventional thermal rearrangement. 

A soln. of mercuric trifiuoroacetate in tetrahydrofuran added dropwise at 0° under N2 during 15 min. to a soln. of geranyl trichloroacetimidate in the same solvent, allowed to warm to room temp, during 1 hr., then pyridine added to complex free mercuric ions product. Y 79%. F. e., also thermal rearrangement in refluxing xylene at 138-9°, s. L. E. Overman, Am. Soc. 96, 597 (1974). 

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