Arenediazonium salts vinylation

Meerwein reactions can conveniently be used for syntheses of intermediates which can be cyclized to heterocyclic compounds, if an appropriate heteroatom substituent is present in the 2-position of the aniline derivative used for diazotization. For instance, Raucher and Koolpe (1983) described an elegant method for the synthesis of a variety of substituted indoles via the Meerwein arylation of vinyl acetate, vinyl bromide, or 2-acetoxy-l-alkenes with arenediazonium salts derived from 2-nitroani-line (Scheme 10-46). In the Meerwein reaction one obtains a mixture of the usual arylation/HCl-addition product (10.9) and the carbonyl compound 10.10, i. e., the product of hydrolysis of 10.9. For the subsequent reductive cyclization to the indole (10.11) the mixture of 10.9 and 10.10 can be treated with any of a variety of reducing agents, preferably Fe/HOAc. 

Sengupta showed that the reaction of bis-arenediazonium salt 91 with vinyl(triethoxy)silane 92 afforded poly(phenylene-vinylene) 93. Although the reaction apparently proceeds through the Heck reaction mechanism, which is described in Section 11.19.4, a part of the step-growth reaction is indeed a transformation of the carbon-silicon bond of 92 to the carbon-carbon bond (Equation (44)). 

Suzuki and other couplings. This Suzuki coupling has been applied to preparation of 2- and 4-arylpyridines. For a synthesis of styrenes the coupling of arenediazonium salts with potassium vinyltrifluoroborate has been developed. The latter is a. stable and efficient vinylating agent. 

Bis(arenediazonium) salts of general structure (12) are reported to crosslink poly(vinyl alcohol) by formation of ether linkages," as shown in equation (13), where the polyol is represented by POH. As in the case of bisazido compounds, crosslinking requires that both diazonium groups react, each with a different polymer. 

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