Nickel catalysis nucleophilic substitution

As mentioned in Sections 3.1.6 and 4.1.3, cyclopropenes can also be suitable starting materials for the generation of carbene complexes. Cyclopropenone di-methylacetal [678] and 3-alkyl- or 3-aryl-disubstituted cyclopropenes [679] have been shown to react, upon catalysis by Ni(COD)2, with acceptor-substituted olefins to yield the products of formal, non-concerted vinylcarbene [2-1-1] cycloaddition (Table 3.6). It has been proposed that nucleophilic nickel carbene complexes are formed as intermediates. Similarly, bicyclo[1.1.0]butane also reacts with Ni(COD)2 to yield a nucleophilic homoallylcarbene nickel complex [680]. This intermediate is capable of cyclopropanating electron-poor alkenes (Table 3.6). 

Michael addition to levoglucosenone with various carbon nucleophiles under base or bis (2,4-pentanedionate)-nickel(II) catalysis gave a series of 4-C-alkyl-4-deoxy branched-chain hexosuloses (30) 2-methylcyclohexanone yielded both its 2- and 6- substituted... 

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