Room-Temperature Hydrodehalogenation of Halogenated Heteropentalenes with One or Two Heteroatoms

Abstract

The pair NaBH(4)-TMEDA as a hydride source and catalytic PdCl(2)(dppf) in THF prove to be an efficient system for the hydrodehalogenation of bromo(chloro)-heteropentalenes with one or two heteroatoms, while Pd(OAc)(2)/PPh(3) is able to reduce reactive haloheteropentalenes, and PdCl(2)(tbpf) allows the removal of the 2-chlorine from a thiophene ring. The reaction conditions tolerate various functional groups, allowing highly chemoselective reactions in the presence of halide, ester, alkyne, alkene, and nitrile substituents and also showing good efficiency in the regioselective hydrodehalogenation of a variety of polyhalogenated substrates.

Site-selective Suzuki–Miyaura coupling of heteroaryl halides – understanding the trends for pharmaceutically important classes

“…2,3-Dibromobenzothiophene can be reacted sequentially via SMC reactions at C2 and then at C3, 141c , 189b , 192 and 2,5-dibromobenzothiophene reacts via SMC reactions at C2. 193 Our data confirms this ( Fig.…”

Total Synthesis of Dictyodendrins by the Gold‐Catalyzed Cascade Cyclization of Conjugated Diynes with Pyrroles

“…This process involved the reaction of 28 with NBS (2.05 equiv) to afford the dibromination product 29 in 54 % yield. The subsequent regioselective debromination of 29 with NaBH 4 in the presence of a catalytic amount of Pd(OAc) 2 afforded the desired monobromide 30 . Finally, the Ullmann coupling of 30 with NaOMe in the presence of CuI afforded the known precursor 14 a , which can be converted into dictyodendrin C in a three‐step sequence as reported by Tokuyama and co‐workers.…”

Total Synthesis of Dictyodendrins A–F by the Gold‐Catalyzed Cascade Cyclization of Conjugated Diyne with Pyrrole

“…[37] or lithiation, [38] we finally succeeded in forming mono-bromide 45 through dibromination of 27 a with NBS (2.05 equiv) at the C2 andC 5p ositions,f ollowedb yC 2-selective mono-debromination of 44 with NaBH 4 in the presence of [PdCl 2 (dppf)]. [39] The Ullmann coupling of 45 with NaOMe in the presence of CuI gave 26 a quantitatively, which has been reported as ap recursoro fd ictyodendrin Cb yT okuyama. [11] We completed the total synthesis of dictyodendrin Ft hrough deprotection of 26 a with BBr 3 and aerobic oxidation.…”