Borane catalyzed transesterification of tert-butyl esters using α-aryl α-diazoesters.

The B(C6F5)3-catalyzed transesterification of a series of 3-alkenyl-oxindoles and other unsaturated tert-butyl esters with aryl-diazo esters is reported. This protocol is facile and generally high yielding proceeding under mild conditions and is remarkably chemoselective leaving the CC bonds intact.

B(C6F5)3-catalyzed hydrogermylation of enones: a facile route to germacycles.

Organogermacycles are important skeletons for medicinal chemistry and materials. Herein, we reported a B(C6F5)3 mediated domino hydrogermylation reaction of enones with dihydrogermanes, affording 21 variants of organogermacycle compounds. These germacyclic compounds were obtained in good to excellent yields (up to 99% yield) under mild reaction conditions.

Catalyst-dependent chemoselective insertion of diazoalkanes into the N-H/C-H/O-H/C-O bonds of 2-hydroxybenzothiazoles.

The control of chemoselective insertions of diazoalkanes into 2-hydroxybenzothiazoles is challenging. Herein, the chemoselective N-H, O-H, C-O or C-H bond insertions of diazoalkanes into 2-hydroxybenzothiazoles are achieved using B(C6F5)3, Rh2(OAc)4 or TfOH as the catalyst. This affords routes to 54 benzothiazole derivatives. These protocols are scalable and demonstrate the complementary nature of Lewis acid, transition metal and Brønsted acid catalyses.

B(C6F5)3-catalyzed cyclopropanation of 3-alkenyl-oxindoles with diazomethanes.

Spirocyclopropane-oxindoles are key motifs in biologically active compounds and are versatile synthetic intermediates. Herein, we report a metal-free, B(C6F5)3 catalyzed cyclopropanation of 3-alkenyl-oxindoles with diazomethanes. This provides 25 variants of spirocyclopropane-oxindole derivatives. These spirocyclopropane-oxindole products were obtained in good to excellent yields (up to 99%) and high diastereoselectivities (up to 20 : 1 d.r.) under mild reaction conditions and could be performed on a gram scale.

Catalytic hydroaminations of alkynes: a facile protocol to vinyl-carbazole derivatives via a frustrated Lewis pair mechanism.

N-Vinylcarbazoles are important skeletons for photoluminescent materials. Herein, a transition metal-free, B(C6F5)3 mediated carbazolation reaction of alkynes is reported, providing 24 variants of N-vinylcarbazole derivatives. These N-vinylcarbazole products were obtained in good to excellent yields (up to 99%) under mild reaction conditions and could be performed on a gram scale.