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Trialkyl phosphines PMe3 and PEt3 catalyze the 1,2‐cis‐diboration of 1,3‐butadiynes to give 1,2‐diboryl enynes. The products were utilized to synthesize 1,1,2,4‐tetraaryl enynes using a Suzuki‐Miyaura protocol and can readily undergo proto‐deborylation. [ABSTRACT FROM AUTHOR]

We report a tri-n-butyl phosphine catalyzed regio- and stereo-selective hydroboration of ynamides to yield (Z)-β-borylenamides in good yields. Surprisingly, a formal cis addition to the triple bond was observed as confirmed by NMR and X-ray crystallography. 31P NMR studies suggest that a zwitterionic vinylphosphonium intermediate is key in the mechanism. The resulting products were further transformed to β-CF3 enamides via stereoretentive trifluoromethylation. [ABSTRACT FROM AUTHOR]

We report an organocatalytic trans hydroboration of 3-substituted-propiolonitriles. In the presence of catalytic amounts of tributylphosphine and pinacolborane, regioselective hydroboration of the internal triple bond proceeded in a stereoselective fashion under mild conditions to afford the corresponding (E)-1,2-vinylcyanoborane derivatives. The mechanism is proposed to occur through a 1,2-phosphine addition instead of a canonical 1,4-conjugate addition pathway. [ABSTRACT FROM AUTHOR]

We report a chemoselective, phosphine‐catalyzed semireduction of primary and secondary propiolamides. In the presence of stoichiometric pinacolborane and catalytic n‐tributylphosphine, a variety of propiolamides were successfully converted to the corresponding acrylamides in excellent yield with (E)‐stereoselectivity. The reaction condition is tolerant of various functional groups including alkene, alkyne, ketone, or ester. Deuterium labeling studies established that the hydride from activated pinacolborane is added to the α‐carbon and the proton on the amide nitrogen is abstracted by the ß‐carbon to furnish the (E)‐acrylamides. DFT calculations revealed a clear energetic driving force for the (E)‐ over the (Z)‐isomer. [ABSTRACT FROM AUTHOR]

We report the first trans phosphinoboration of internal alkynes. With an organophosphine catalyst, alkynoate esters and the phosphinoboronate Ph2P‐Bpin are efficiently converted into the corresponding trans‐α‐phosphino‐β‐boryl acrylate products in moderate to good yield with high regio‐ and Z‐selectivity. This reaction operates under mild conditions and demonstrates good atom economy, requiring only a modest excess of the phosphinoboronate. X‐ray crystallography experiments allowed structural assignment of the unprecedented and densely functionalized (Z)‐α‐phosphino‐β‐boryl acrylate products. [ABSTRACT FROM AUTHOR]