Bivalent synthons

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... 

Scheme 2.60 Bivalent methylene synthons as conjunctive reagents...

Scheme 2.62 7,7-Bivalent carbonyl synthons and corresponding reagents...

Scheme 5.7 Examples for synthetic equivalents of 1,1-bivalent conjunctive synthons...

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