THF-enabled PtBr2-catalyzed desymmetric hydrogenative [3 + 2] cycloaddition of 2-alkynylbenzaldehyde-tethered cyclohexadienones†
*b
and
Weidong
Rao
*a
Abstract
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.
![Graphical abstract: THF-enabled PtBr2-catalyzed desymmetric hydrogenative [3 + 2] cycloaddition of 2-alkynylbenzaldehyde-tethered cyclohexadienones](/en/Image/Get?imageInfo.ImageType=GA&imageInfo.ImageIdentifier.ManuscriptID=D2QO00593J&imageInfo.ImageIdentifier.Year=2022)
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