Syntheses, Structures, and Reactivity of 2,5-Diboryl-1-alkylpyrroles and Di(1-alkyl-2-pyrrolyl)boranes

Abstract

Keywords: Boranes / 1-Alkylpyrroles / Porphyrinogenes / Lithiation / Tin-boron exchangeReactions of 2,5-dilithiated 1-methylpyrrole (1a) with the aryloxy-boryl derivative 2e. Reacting monolithiated 1-methyl-and 1-benzylpyrroles with Cl 2 BNiPr 2 yields the di(2-ClB(NR 2 ) 2 lead to the novel 2,5-diboryl-1-methylpyrroles 2a and 2b. Accordingly, 2,5-diboryl-1-benzylpyrrole 2d is pyrrolyl)boranes 3e and 3f, respectively. NMR and MS data are in agreement with the compositions of the compounds, obtained. 1a and Cl 2 BNiPr 2 form the aminochloroborylsubstituted derivative 2c and the di(5-boryl-2-which are confirmed by X-ray structure analyses for 2a, 2b, 2d, und 3e. pyrrolyl)borane 4 in 29% and 15% yield, respectively. The 2,5-distannyl-1-methylpyrrole 1c is used for the synthesis of is reduced to the dianion E. As a first example of a tetra-

Design and Synthesis of Stimuli-Responsive Conjugated Polymers Having Azobenzene Units in the Main Chain

“…N,N-Dimethylformamide (DMF) was distilled over calcium hydride. 4,4′-Diiodoazobenzene (1a), 14 2,2′,5,5′tetrahexyl-4,4′-diiodoazobenzene (1b), 14 1,4-diethynyl-2,5-dihexylbenznene (2b), 28 2,5-bis(trimethylstannyl)thiophene (4a), 29 2,5-bis(trimethylstannyl)furan (4b), 29 2,5-bis(trimethylstannyl)pyrrole (4c), 30 and 2,5-bis(trimethylstannyl)pyridine (4d), 31 were synthesized according to the literature. 1,4-Diethynylbenzene (2a) was purchased from Tokyo Kasei, Co. and recrystallized from hexane.…”

Transition‐Metal‐Free Heterocyclic Carbon‐Boron Bond Formation

“…Treatment of 1-methylpyrrole with excess of n BuLi and TMEDA affords 2,5-dilthio-1-methylpyrrole, which reacted with ClB(NMe 2 ) 2 to give 2,5-bis[bis(dimethylamino)boryl]-1-methylpyrrole in 47 % yield (Scheme 7a). [49] Later the author engaged a similar approach for the synthesis of bis-heteroaryl boranes (Scheme 7b). [50] In 2007 the Klingensmith and Moniz group reported the synthesis of 4-methyl-2-thiopheneboronic anhydride (Scheme 7c).…”

“…In 1999 the Siebert group introduced a dehydrogenative lithiation‐borylation approach for the synthesis of borylated N ‐methylpyrrole. Treatment of 1‐methylpyrrole with excess of n BuLi and TMEDA affords 2,5‐dilthio‐1‐methylpyrrole, which reacted with ClB(NMe 2 ) 2 to give 2,5‐bis[bis(dimethylamino)boryl]‐1‐methylpyrrole in 47 % yield (Scheme 7a) [49] . Later the author engaged a similar approach for the synthesis of bis‐heteroaryl boranes (Scheme 7b) [50] .…”