Palladium-Catalyzed 1,3-Difunctionalization Using Terminal Alkenes with Alkenyl Nonaflates and Aryl Boronic Acids

A Pd-catalyzed 1,3-difunctionalization of terminal alkenes using 1,1-disubstituted alkenyl nonaflates and arylboronic acid coupling partners is reported. This transformation affords allylic arene products that are difficult to selectively access using traditional Heck cross-coupling methodologies. The evaluation of seldom employed 1,1-disubstituted alkenyl nonaflate coupling partners led to the elucidation of subtle mechanistic features of π-allyl stabilized Pd-intermediates. Good stereo- and regioselectivity for the formation of 1,3-addition products can be accessed through a minimization of steric interactions that emanate from alkenyl nonaflate substitution

Origin of High <i>E</i>‑Selectivity in 4‑Pyrrolidinopyridine-Catalyzed Tetrasubstituted α,α′-Alkenediol: A Computational and Experimental Study

We have developed 4-pyrrolidinopyridine catalysts for the geometry-selective (<i>E</i>-selective) acylation of tetrasubstituted α,α′-alkenediols. To elucidate the major factors of the high geometry selectivity, experimental and computational studies were carried out. The control experiments with respect to the substituent of the substrate indicated the fundamental hydrogen bonding of the acidic hydrogen of NHNs and the <i>Z</i>-OH in the substrate. Comparison between <i>C</i>₂- and <i>C</i>₁-symmetric catalysts exhibited the necessity of the <i>C</i>₂-symmetric catalyst structure. The computationally proposed transition state (TS) model well explained the experimental results. Whereas the fundamental NH/amide-CO and the two-point free-OH/acetate anion hydrogen bonds stabilize the transition state (TS), affording the <i>E</i>-product, the steric repulsion between the N-protecting group and the amide side chain destabilizes TS, affording the <i>Z</i>-product. The role of the two amide side chains of the catalyst in a <i>C</i>₂-symmetric fashion is the enhancement of the molecular recognition ability through the additional hydrogen bond in a cooperative manner