Ylide formation carbene synthesis, diazo compounds

As with any modern review of the chemical Hterature, the subject discussed in this chapter touches upon topics that are the focus of related books and articles. For example, there is a well recognized tome on the 1,3-dipolar cycloaddition reaction that is an excellent introduction to the many varieties of this transformation [1]. More specific reviews involving the use of rhodium(II) in carbonyl ylide cycloadditions [2] and intramolecular 1,3-dipolar cycloaddition reactions have also appeared [3, 4]. The use of rhodium for the creation and reaction of carbenes as electrophilic species [5, 6], their use in intramolecular carbenoid reactions [7], and the formation of ylides via the reaction with heteroatoms have also been described [8]. Reviews of rhodium(II) ligand-based chemoselectivity [9], rhodium(11)-mediated macrocyclizations [10], and asymmetric rho-dium(II)-carbene transformations [11, 12] detail the multiple aspects of control and applications that make this such a powerful chemical transformation. In addition to these reviews, several books have appeared since around 1998 describing the catalytic reactions of diazo compounds [13], cycloaddition reactions in organic synthesis [14], and synthetic applications of the 1,3-dipolar cycloaddition [15]. 

The most important methods for the synthesis of thiane and thiepane derivatives involve sulfonium ylide formation. The most graceful and effective of these is the intramolecular cyclization of carbenes derived from diazocarbonyl and diazodicarbonyl compounds. In some cases, the latter provide stable sulfonium ylides. Thus, ylides 455 ( = 1 R = Et, Ph) were produced on heating diazo compounds 456 ( = 1 R = Et, Ph) in 62 and... 

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