A THF-enabled PtBr₂-catalyzed desymmetric hydrogenative [3 + 2] cycloaddition of 2-alkynylbenzaldehyde-tethered cyclohexadienones has been developed. The protocol provides a highly functionalized 6-7-6 polycyclic skeleton with four contiguous stereocenters in good to excellent yields of up to 97% yield and with exclusive exo-selectivity. The suggested cascade reaction pathway delineates a rare instance in platinum catalysis of the involvement of an in situ formed Pt-bound benzopyrylium species that participates in a Huisgen-type [3 + 2] cycloaddition with an electron-deficient alkene tether in the highly reactive organometallic intermediate. It also offers the first example of a metallocarbene species generated in this manner which undergoes hydrogenation with THF as the hydride transfer source. The synthetic utility of the catalytic method was exemplified by the late-stage stereoselective modification of the steroids estrone and estradiol under mild reaction conditions.

中文翻译：

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THF 使 PtBr2 催化的 2-炔基苯甲醛系链环己二烯酮的不对称氢化 [3 + 2] 环加成

已经开发了 THF 启用的 PtBr ₂催化的不对称氢化 [3 + 2] 环加成 2-炔基苯甲醛系环己二烯酮。该协议提供了一个高度功能化的 6-7-6 多环骨架，具有四个连续的立体中心，具有高达 97% 的产率和独特的外选择性。所建议的级联反应途径描绘了铂催化原位参与的罕见实例形成了与高反应性有机金属中间体中的缺电子烯烃系链进行Huisgen型[3 + 2]环加成的Pt结合的苯并吡喃物种。它还提供了以这种方式产生的金属卡宾物质的第一个例子，它以 THF 作为氢化物转移源进行氢化。在温和的反应条件下，类固醇雌酮和雌二醇的后期立体选择性修饰证明了催化方法的合成效用。