Cyclopropylcarbene complexes synthesis

The presence of a cyclopropyl moiety in the carbene complexes makes them useful for synthesis. The cyclopropylcarbene complexes 95 undergo a cycloaddition reaction with alkynes to give the cyclopentenones 96 [51]. The reaction course is explained as being metallacyclopentene fragmentation. (Scheme 34)... 

Cyclopropylcarbene complexes of the type L M=C(XR )R2 (X = O, S R1 = alkyl, aryl R2 = cyclopropyl) having a stabilizing heteroalkyl (XR1) group on the electrophilic carbene ligand (Scheme 3) have found widespread application in organic synthesis. These so-called Fischer carbene complexes are best known via their group 6 transition metal carbonyl complexes (CO)5M=(OR )R2(M = Cr, Mo, W)132. Much less abundant are the Schrock-type cyclopropylcarbene complexes L M=CR R2 where no heteroatom is bound to the carbene carbon atom133. 

Cyclopropyl-substituted transition-metal carbene and carbyne complexes, especially as cyclo-propylidene- or as cyclopropylcarbene complexes, have been used as synthetic building blocks with or without ring opening. Examples of cyclopropane synthesis via decomplexation are described in Section 1.A.5.2.6. 

Cycloadditions. Pyrolysis of 0-alkynyl cyclopropylcarbene complexes generates fused cyclopentenones. This transformation has been exploited in a synthesis of a vitamin Dj synthon. ... 

Ring-opening reactions of cyclopropylcarbene and -carbyne complexes have been used in the synthesis of open-chain products, cyclopentenones, cyclopentadienones, cyclohepta-... 

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