Meyer-Schuster Rearrangement And Tandem Reaction Studies Based On Meyer-Schuster Rearrangement

?,?-Unsaturated carbonyl compounds and nitrogen-containing derivatives, including oximes, nitriles, amides, etc., are an important class of organic compounds. Due to bifunctional and dipolar nature, they are versatile building blocks for diverse functional group transformations and carbon-carbon/carbon-heteroatom bond formations in organic synthesis. Furthermore, this type of structures also serves as the core skeletons of a variety of natural products, pharmaceuticals and materials. The protocol for synthesis of ?,?-unsaturated carbonyl compounds and other nitrogen derivatives via Meyer-Schuster rearrangement (M-S rearrangement) and the cascade reaction based on the rearrangement from readily available propargylic alcohols is believed to be facile, efficient and highly atom economic. Thus, this synthetic strategy has attracted considerable attention. Exploration of effective catalysts for M-S rearrangement and synthesis of nitrogen-containing compounds using M-S rearrangement-based cascade reaction are two hot research topics in this field, and still in great need.In the dissertation, we have developed a green catalyst, silicon gel supported phosphomolybdic acid (PMA/SiO2), for M-S rearrangement. The new catalyst is proved to be inexpensive, easy-preparation, environmentally benign and readily recycled. We have also established a "one-pot" approach to preparation of ?,?-unsaturated oximes and nitrils from propargylic alcohols and hydroxylamine hydrochloridc. With the regulation of dehydrating promoter, oxime or nitrilc can be obtained selectively.The dissertation mainly focuses on the following aspects:(1) We first evaluated the catalytic effects of several supported heteropoly acids on the M-S rearrangement. In the presence of the optimized catalyst PMA/SiO2, various secondary and tertiary propargylic alcohols transformed to the corresponding a,p-unsaturated ketones, aldehydes or esters smoothly in moderate to excellent yields with high stereo selectivity (18 cases). Moreover, the supported catalyst could be readily recovered and recycled.(2) We explored the preparation of ?,?-unsaturated oximes from propargylic alcohols with a two-step one-pot strategy based on the M-S rearrangement. Under the optimized condition of 30 mol% PTSA/DCE/90?, a variety of propargylic alcohols could react with hydroxylamine hydrochloride giving the desired ?,?-unsaturated oximes in high yields via a cascade process (12 cases). By adding dehydrating promoter TsCl to the same reaction system, ?,?-unsaturated nitriles could also be obtained in one pot with good substrate scope (18 cases). The notable features of the new method include readily available starting material, green and safe nitrogen source, inexpensive catalyst and reagent, convenient operation and suitable for large-scale preparations. In addition, the conversion of propargylic alcohols to ?,?-unsaturated nitriles under microwave irradiation was also examined, and the preliminary results show that the target nitriles could be attained in moderate yield when using the silicone gel supported sulphuric acid as catalyst.(3) The preliminary study has also been conducted to explore the synthesis of ?,?-unsaturated amides from propargylic alcohols via M-S rearrangement and Beckmann rearrangement.