Palladium−Iminophosphine-Catalyzed Alkynylstannylation of Alkynes

Abstract

A palladium complex coordinated by an iminophosphine ligand was found to catalyze the addition of alkynylstannanes to a carbon-carbon triple bond of various alkynes in moderate to good yields with exclusive syn selectivity. The alkynyl group in the stannanes was attached mainly to the internal carbon of terminal alkynes, except for 1-alkyn-3-ones and alkynoates, where the alkynyl group was connected to the terminal carbon. Steric bulk of the ligand markedly influenced on the regioselectivity and reaction rate: an iminophosphine with a bulkier imino moiety accelerated the alkynylstannylation with higher regioselectivity. On the basis of these observations, the mechanism of the present reaction is discussed.

Biaryl synthesis using highly stablearyl[2-(hydroxymethyl)phenyl]dimethylsilanes and aryl iodides under fluoride-free conditions

“…Those having an electron-donating methyl and free amino group at the paraposition were also isolated quantitatively (entries 8 and 9). Meta-substitution did not affect the reaction (entries [10][11][12]. It is worth noting that t-BuMe 2 Si-ether, which is easily cleaved under the conventional fluoride activation protocols, survives completely (entry 12).…”

“…Anhydrous DMSO was purchased from Aldrich and used without further purification. N-(2-Diphenylphosphinobenzylidene)cyclohexylamine (4) was prepared according to the reported procedure [10].…”

Synthesis of Trisubstituted Alkenylstannanes through Copper‐Catalyzed Three‐Component Coupling of Alkylboranes, Alkynoates, and Tributyltin Methoxide

“…[2] Among the routes to trisubstituted alkenylstannanes, transition-metal-catalyzed stereoselective carbostannylation of internal alkynes with organostannanes is the most straightforward and attractive (Scheme 1a). [3][4][5][6][7] This catalytic method allows the simultaneous formation of CÀC and CÀSn bonds. Shirakawa, Hiyama, and co-workers developed the palladium-or nickel-catalyzed carbostannylation of internal alkynes with allyl-, acyl-, and alkynylstannanes.…”

“…Shirakawa, Hiyama, and co-workers developed the palladium-or nickel-catalyzed carbostannylation of internal alkynes with allyl-, acyl-, and alkynylstannanes. [3] These methods are useful for the preparation of trisubstituted alkenylstannanes, but require tedious preparation of the organostannane reagents. Additionally, sp 3 -alkylstannanes have not been used for the introduction of alkyl groups.…”

“…[3] These methods are useful for the preparation of trisubstituted alkenylstannanes, but require tedious preparation of the organostannane reagents. Additionally, sp 3 -alkylstannanes have not been used for the introduction of alkyl groups. [5] Furthermore, the regioselectivity is not always reliable, especially as the regiocontrol is generally difficult even with alkynes that are desymmetrized by electronic effects.…”