Studies on Characteristic Reactions in the Chalcogeno -Baylis -Hillman Reactions

In order to overcome the drawback of the bayles - hillman reaction, “the slow rate ”we developed the chalcogemde- ticl_4 -mediated tandem Michael-aldol reactions. the reactions had beendeemed to be a chalcogene version of the bayles - hillman reactionbecause the bayles - hillman adducts were given after purification of the products by the preparativeTLC on silica gel. However，initial products were α-chloromethyl aldols and were dehydrochlorinated during purification bythe preparative TLC. the reactions of S-ethyl thioacrylate and keto esters gave much better resultsthan the bayles - hillman reactions of ten. the reactions of acetylenic ketones and esters producedα-chloromethylene aldols. The chalcogenides necessary for The reactions of α,β-unsaturatedThe reactions of acetylenic ketones and esters and α-keto esters did not occur when tertiaryamines used as a catalyst instead of a Chalcogenide and ticl_4 .We next studied the reaction inwhich a chalcogenide worked as Lewis base and found that sulfanyl substituent intramolecularlyadded to an enone to form a cychc sulfomum betaine. The tandem Michael-aldol reactions of 1-[2-(methylsulfanyDphenyl)]prop-2-en-1-one or the seleno congener with aldehydes in the presence ofbf_3 e_2o gave the bayles - hillman adduct and onium salt，and 3-(α-hydroxybenzyl) selenochromanone from the seleno congener。

In order to overcome the drawback of the Baylis-Hillman reaction, "the slow rate," we developed the chalcogemde-TiCl_4-mediated tandem Michael-aldol reactions. The reactions had been deemed to be a chalcogene version of the Baylis-Hillman reaction, because the Baylis-Hillman adducts were given after purification of the products by the preparative TLC on silica gel. However, the initial products were α-chloromethyl aldols and were dehydrochlorinated during purification by the preparative TLC. The reactions of S-ethyl thioacrylate and keto esters gave much better results than the Baylis-Hillman reactions of ten. The reactions of acetylenic ketones and esters produced α-chloromethylene aldols. The chalcogenides were necessary for the reactions of α,β-unsaturated esters. The reactions of acetylenic ketones and esters and α-keto esters did not occur when tertiary amines were used as a catalyst instead of a Chalcogenide and TiCl_4.We next studied the reaction in which a chalcogenide worked as Lewis base and found that sulfanyl substituent intramolecularly added to an enone to form a cychc sulfomum betaine. The tandem Michael-aldol reactions of 1- [2-(methylsulfanyDphenyl]prop-2-en-1-one or the seleno congener with aldehydes in the presence of BF_3・E_2O gave the Baylis-Hillman adduct and onium salt, and 3-(α-hydroxybenzyl) selenochromanone from the seleno congener.