Bronsted Acid-catalyzed Ortho-hydroxy(mercapto) Benzyl Alcohol-involved Cyclizations

In the first chapter,the racemic reaction and the asymmetric reaction of ortho-quinone methides were introduced.At the same time,we also introduced the goal and the content of the research.In the second chapter,the first catalytic asymmetric inverse-electron-demand(IED)oxa-Diels-Alder reaction of ortho-quinone methides generated in situ from ortho-hydroxybenzyl alcohols has been established.By selecting 3-methyl-2-vinylindoles as a class of competent dienophiles,this approach provides an efficient strategy to construct enantioenriched chroman framework with three adjacent stereogenic centers in high yields and excellent stereoselectivities(up to 99% yield,>95:5 dr,99.5:0.5 er).The utilization of ortho-hydroxybenzyl alcohols as precursors of dienes and 3-methyl-2-vinylindoles as dienophiles,as well as the hydrogen-bonding activation mode of the catalyst to the substrates will meet the great challenges in catalytic asymmetric IED oxa-Diels-Alder reactions.In the third chapter,a catalytic chemo-,(E/Z)-and enantioselective cyclization of ortho-hydroxybenzyl alcohols with dimedone-derived enaminones has been established,which not only realized a chemoselective C1,2-cyclization of enaminones,but also achieved the catalytic asymmetric construction of biologically important tetrahydroxanthene framework with high(E/Z)-and enantioselectivities(all >95:5 E/Z,up to 98% yield,97:3 er).This approach not only represents the first catalytic asymmetric C1,2-cyclization of enaminones with ortho-hydroxybenzyl alcohols,but also provides an efficient strategy for constructing oxygenous heterocyclic frameworks with optical purity.In the fourth chapter,chemodivergent [5+2] cyclization and hydroxysulfenylation reactions of ortho-mercaptobenzyl alcohols with 3-alkyl-2-vinylindoles and styrenes have been established in the presence of Br?nsted acid,which provided efficient methods for constructing benzoxathiepine scaffold and synthesizing hydroxy sulfides at good yields and excellent diastereoselectivities.