Synthesis Of Trisubstituted Olefins Featuring The Regio-and Stereoselective Addition Of Heteroatom-Substituted Acetylenes

Trisubstituted alkenes are important building blocks in organic chemistry. Therefore, it is highly desirable to develop new efficient and general methods for the regio-and stereoselective synthesis of trisubstituted alkenes. By using hydrothiolation or hydroalkynylation reaction, some regio-and stereoselective methods for accessing trisubstituted alkenes has been realized in this dissertation, which mainly consists of two parts:Firstly, a K2CO3-promoted regio-and stereoselective hydrothiolation of alkynyl halides has been realized for the first time, giving rise to (Z)-(3-halo alkenyl sulfides in good yields with excellent regio-and stereoselectivity under quite mild reaction conditions. Notably, by taking advantage of the different reactivity of C-X and C-S bonds in the cross-coupling reactions, an operationally simple and general protocol for the production of stereodefined trisubstituted olefins from (Z)-β-halo alkenyl sulfides has been developed, thus providing a novel procedure for the synthesis of trisubstituted alkenes and related natural products.Secondly, a Pd-catalyzed regio-and stereoselective hydroalkynylation of ynamides has been achieved, providing trisubstituted enamides in good yields and excellent stereoselectivity. The reaction proceeds under mild reaction conditions and tolerates a number of functional groups, thus enabling a highly atom-economic procedure for the access of trisubstituted olefins. It represents a significant advance in the hydroalkynylation of nonterminal alkynes.