Metal-mediated rearrangements copper

Julian, R. R., May, J. A., Stoltz, B. M., Beauchamp, J. L. Gas-Phase Synthesis of Charged Copper and Silver Fischer Carbenes from DIazomalonates Mechanistic and Conformational Considerations In Metal-Mediated Wolff Rearrangements. J. Am. Chem. Soc. 2003, 125, 4478 486. 

Various functionalized alkynes can be submitted to carbocupration reactions, such as alkoxyalkynes,150 alkynyl carbamates,151 acetylenic orthoesters,152 and thioalkynes.153 The carbocupration of orthoesters, for example, 204, has been used to prepare a-substituted esters of the type 206 by acidic hydrolysis of the adduct 205 (Scheme 51).152 This allows the formation of regioisomers that are not accessible by copper-mediated addition to acetylenic esters. A stereoselective synthesis of trisubstituted alkenes has been described by Normant et al.lSd> starting from phenylthio-acetylene 207. Carbocupration with lithium di- -butylcuprate affords the intermediate 208 which, upon addition of /z-butyllithium, undergoes a 1,2-metalate rearrangement to the vinylcuprate 209. The latter can be trapped with various electrophiles, for example, ethyl propiolate, providing product 210 with complete regio- and stereocontrol. 

The metal-catalyzed decomposition of diazo compounds 603 provides access to a variety of cephem derivatives (Scheme 30). Copper-mediated cyclization of diazo ketone 603 (R = Et) gives 3-oxocepham through sulfo-nium ylide formation followed by j8-elimination (80H1999). The formation of cephem derivatives 604 and 605 presumably involves the intermediacy of ylide 606 (R = Ac, ArCH2) and its subsequent rearrangement. A more sophisticated mechanism is proposed for the formation of 607 and 608 (83H205). 

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