Multicoupling reagents

Enamines from ketones can react with double Michael multicoupling reagents to give, after aqueous workup, mono- and bicyclic ketones, products of a,a -annulation55-59. 

The various synthons considered up to this point allow the formation of a single skeletal bond. Bivalent synthons, i.e., those having two reactive positions, would allow for the simultaneous or sequential formation of two skeletal bonds. An example can be found in Scheme 2.38 (see p. 29), where an acetylene has been placed as a C2-unit between two other synthons. Such bivalent synthons have been referred to by Trost [109] as conjunctive reagents, and by Seebach [110] as multicoupling reagents. The simplest conjunctive reagent... 

In addition, Seebach has extended his work on nitroallyl pivalates as multicoupling reagents (Vol. 6, p. 208) and has now published the synthesis and reactions of the nitroallyl pivalates (22) and (23) and the chloride (24) (Scheme 35). These new reagents furnish adducts with a variety of nucleophilic species and, as with previously reported analogues, the acceptor properties of the nitro-group may be further exploited. 

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