Intermolecular carbometalation

The intermolecular carbometallation reaction catalyzed by transition metals from groups 8 to 11 has been fully investigated during the last decade. Many examples have been reported in the literature concerning different metals in order to create C-C bonds. Overview of this powerful method will be given as exhaustively as possible and carbometallation reactions will be classified according to unsaturated systems. 

Intermolecular carbometallations are typically accomplished with organolithiums however, dia-stereocontrolled intramolecular carbometallation can be attained with appropriate Grignard reagents, as exemplified in Scheme 88, the suprafacial and 5-exo-trig closure of ( )-6-bromo-3-methyl-1 -trimethylsi-lyl-1-hexene (267) to fraru-l-methyl-2-(trimethylsilyl)methylcyclopentane (268).203... 

Vicinal Difunctionalization of Alkenes and Acetylenes via Intermolecular Carbometallation 225... 

This chapter is intended to highlight recent results in the fields of intra- and intermolecular carbometallation, but we will concentrate only on the chemistry of lithium and zinc derivatives. Although the Group IV metallocene-mediated reductive cyclizations of enynes [36] and dienes [36], and the use of transition metals of Group VIII, as well as the more recent development of the organolanthanide chemistry [37] followed by selective reaction with different electrophiles [36], represent an important methodology for the construction of polysubstituted carbocycles, they will not be addressed here. 

The addition of an organometallic to an unactivated olefin is generally difficult to control since such an addition may lead to polymerization of the olefin unless the final organometallic adduct is stabilized, or has a structural modification. Thus, no general reaction for the intermolecular carbometallation of alkenes is known, although since the last review concerning this topic [3], many relevant papers have appeared. 

Scheme 8.86 Intermolecular carbometallation and subsequent cyclization of o-alkynylaniline derivatives [500].

Scheme 10.38 Protocol for the copper-catalyzed directed intermolecular carbometallation of...

Hayashi et al. [114] also reported the possibiUty of an intermolecular carbometallation of alkynes with arybhodium species. Thus, it was confirmed experimentally that the formation of N-heterocychc amides 400 was most probably initiated by an intermolecular carborhodation of the triple bond in 399 to yield the intermediate 401 (Scheme 10.137). 

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