Alkenesulfonyl chlorides

Arenesulfonyl chlorides as well as alkenesulfonyl chlorides react with vinylarenes in the presence of RuCl2(PPh3)3 and 1 molar equiv. of EtjN to form a,j8-unsaturated sulfones in 70-90% yields. The reaction mechanism for the ruthenium(II) catalyzed reaction involves a free-radical redox-transfer chain process as outlined below ... 

Scheme 13,6 Ruthenium-catalyzed addition of alkenesulfonyl chlorides.

Stork and Borowitz36 were able to rule out an alternative mechanism, in which an initially formed mesylated enamine underwent cyclization, by preparing the mesylated species (87) and showing that it did not yield the cycloadduct (equation 67). Borowitz36 also demonstrated that only electron-rich olefins (such as enamines, ketene dialkyl acetals, etc.) give [2 + 2] cycloadducts when the sulfene is generated from alkenesulfonyl chlorides and triethylamine, and no cycloadduct was formed in the presence of cyclohexene, ethoxyacetylene or anthracene. 

In 1985, Kamigata et al. [61] reported on ruthenium-catalysed alkenylations of alkenes, employing alkenesulfonyl chlorides. High yields of isolated product were obtained with [RuCl2(PPh3)3] (94) as catalyst in benzene as solvent (Scheme 10.34). Importantly, no base was required for the coupling process, for which a radical-based mechanism was proposed. 

Scheme 10.34 Ruthenium-catalysed alkenylation with alkenesulfonyl chloride 95.

Dubbaka, S.R. and Vogel, P. (2005) Palladium-catalyzed desulfltative Mizoroki-Heck coupling of sulfonyl chlorides with mono- and disubstituted olefins rhodium-catalyzed desulfitative Heck-type reactions under phosphine- and base-free conditions. Chem. Eur. J., 11, 2633 1. Kamigata, N., Ozaki, J.-i., and Kobayashi, M. (1985) Reaction of alkenesulfonyl chlorides with olefins catalyzed by a ruthenium(ll) complex. A novel method for synthesis of ( , )- ,4-diaryl-... 

The overall process involving addition of a-bromomethanesulfonyl bromide to olefins and subsequent dehydrobromination followed by base-promoted viny-logous Ramberg-Backlund reaction constitutes a three-step transformation of olefins into 1,3-dienes (Scheme 14) [107]. Conjugated dienes are also available from the Ru(II)-catalyzed reaction of alkenesulfonyl chlorides with olefins [108],... 

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