Enantioselective Synthesis of 1,3-Disubstituted 1,3-Dihydroisobenzofurans via a Cascade Allylboration/Oxo-Michael Reaction of <i>o</i>‑Formyl Chalcones Catalyzed by a Chiral Phosphoric Acid

The first chiral Brønsted acid-catalyzed asymmetric cascade allylboration/oxo-Michael reaction between o-formyl chalcones and allylboronate has been successfully discovered, which afforded chiral 1,3-disubstituted 1,3-dihydroisobenzofurans with a yield, diastereoselective ratio (dr) and enantioselective excess (ee) up to 94%, 2.5:1, and 98%, respectively. In addition, 2,3-dienylboronic pinacol ester was also applied into this cascade reaction with good catalytic results.本研究首次成功实现了手性布朗斯特酸（chiral Brønsted acid）催化的邻甲醛查尔酮与烯丙基硼酸酯（allylboronate）之间的不对称级联烯丙基硼化/氧杂-Michael反应，所得手性1,3-二取代1,3-二氢异苯并呋喃产物的最高收率可达94%，非对映选择性比例（dr）可达2.5:1，对映体过量值（ee）最高为98%。此外，将2,3-二烯基硼酸频哪醇酯应用于该级联反应中，亦可获得良好的催化效果。