Nucleophilic substitution diene conjugation, allylic intermediates

Allylic and dienyl sulfones have been prepared by conjugate addition to 1,3-dienes ". Phenylsulfonyhnercuration of conjugated dienes gives mercury adducts which can be treated with base to afford phenylsulfonyldienes. 2-(Phenylsulfonyl)-l,3-dienes can be stereo- and regioselectively functionalized via Michael addition of nucleophiles to give allylic sulfones. A key intermediate in the synthesis of a Monarch butterfly pheromone 4 was prepared by BackvaU and Juntunen by alkylation and subsequent palladium-catalyzed substitution of the allylic sulfone formed by Michael addition of dimethyl malonate to 2-(phenylsulfonyl)-l,3-butadiene (equation 10). 

Vinyl substitutions on alkenes not having their double bonds conjugated with carbonyl groups often proceed more rapidly and give better product yields when the reactions are conducted in the presence of an unhindered secondary amine. Conjugated and nonconjugated dienes are usually only minor products in these cases. The major products normally are allylic amines obtained by nucleophilic attack of the secondary amine upon the ir-allylpalladium intermediates. Since allylic amines may be quatemized and subjected to the Hoffmann elimination, this is a two-step alternative to the direct vinyl substitution reaction.90... 

The additives of water can serve as mechanistic probes and aid in obtaining true mechanistic understanding in some organocatalytic reactions [123]. The water is nucleophile in palladium-catalyzed oxidative carbo-hydroxylation of allene-substituted conjugated dienes [124]. This is an example of Pd- catalyzed oxidation leading to C -C bond formation in water with subsequent water attack on a (rr-allyl) palladium intermediate. The different effect of the water concentration on the intra- and extra-diol oxygenations of 3,5-di-tert-butylcatechol with O2, catalyzed by FeC in tetrahydrofuran-water indicates that the intermediates for two reactions are different (model for Catechol-2,3-dioxygenases) [125]. 

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