Rhodium/palladium-Catalyzed Carbon-Carbon Bond Forming Reactions Of Arylboronic Acids With Organic Electrophiles

This dissertation consists of two parts: 1) Rhodium-catalyzed reactions of a,β-unsaturated carbonyl compounds with arylboronic acids; 2) Developing an ionic medium for ligandless-palladium-catalyzed Suzuki and Heck coupling. 1. Rhodium-catalyzed reactions of a,p-unsaturated carbonyl compounds witharylboronic acidsWe reported, for the first time, rhodium-catalyzed Heck-type reaction of arylboronic acids with α,β-unsaturated esters or nitrile under aqueous conditions by tuning the steric environment around catalytic species rhodium(I). The olefin structure displayed a marked effect on the reaction. Parent acrylates reacted smoothly, but substituted acrylates gave products in low yield or remained untouched, indicting steric factors played a critical role in the reaction. Our results clearly demonstrate the hydrolysis us. β-H elimination of alkylrhodium could be finely tuned and should promise new rhodium-based catalysis.As a part of our continuing exploration of catalysis with the sterically sensitive rhodium-phosphine biphasic system, we investigated the possibility of switching the Heck-type coupling to 1,2-addition of arylboronic acids to α, β-unsaturated aldehydes. Unexpectedly, we uncovered a novel self-conjugate reduction, cross-coupling tandem reaction of arylboronic acids with cinnamaldehyde and analogues. The novel reaction through a novel three-membered metallocyclopropanone intermediate.During further exploration of catalysis with the rhodium-phosphine biphasic system, we investigated the possibility of the Heck-type coupling of arylboronic acids with ,P-unsaturated amides. N,N-dimethylacrylamide exhibited similar reactivity to butyl acrylate, the Heck product was smoothly obtained with a 2:1 ratio of olefin to boronic acid. We have also successfully developed a procedure for 1,4-conjugate addition through optimization of the reaction condition in the rhodium-phosphine biphasic system.2. Developing an ionic medium for ligandless-palladium-catalyzed Suzuki and Heck couplingWe uncovered high-melting-point alkylammonium tetrafluoroborates melt with water or toluene to form biphasic mixtures at much lower temperatures than their normal melting points, thus could serve as green reaction media for Suzuki and Heck couplings. Advantages of using the aqueous-ammonium biphasic catalytic system include: (1) working well with a ligandless palladium catalyst; (2) solving the solubility problem of organic substrates and (3) simplifying work-up procedures for both separation of products and recycling of reaction media.