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

Abstract

Reactions of 2,5‐dilithiated 1‐methylpyrrole (1a) with ClB(NR2)2 lead to the novel 2,5‐diboryl‐1‐methylpyrroles 2a and 2b. Accordingly, 2,5‐diboryl‐1‐benzylpyrrole 2d is obtained. 1a and Cl2BNiPr2 form the aminochloroboryl‐substituted derivative 2c and the di(5‐boryl‐2‐pyrrolyl)borane 4 in 29% and 15% yield, respectively. The 2,5‐distannyl‐1‐methylpyrrole 1c is used for the synthesis of the aryloxy‐boryl derivative 2e. Reacting monolithiated 1‐methyl‐ and 1‐benzylpyrroles with Cl2BNiPr2 yields the di(2‐pyrrolyl)boranes 3e and 3f, respectively. NMR and MS data are in agreement with the compositions of the compounds, which are confirmed by X‐ray structure analyses for 2a, 2b, 2d, und 3e.

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 Polymer 5a. A solution of DMF (8.0 mL) containing 1b (462 mg, 0.600 mmol), 4a (251 mg, 0.612 mmol), and PdCl 2(PPh3)2 (8.4 mg, 0.012 mmol) in a 30 mL round-bottom flask charged with nitrogen was stirred at 110°C for 48 h. The reaction mixture was poured into 300 mL of methanol.…”

Syntheses and Structures of Novel λ3,λ3-Phosphanylalumanes Fully Bearing Carbon Substituents and Their Substituent Effects

“…The reaction of (t-Bu)2AlBr [21] with Mes2PLi [22] afforded a λ 3 ,λ 3 -phosphanylalumane 1 quantitatively, judged by 31 P NMR spectroscopy (Scheme 1a). Conversely, the use of (C6F5)2AlCl•0.5(toluene) [23] as an aluminum source in a hexane solution afforded an LiCl complex, λ 4 ,λ 4 -phosphanylalumane 2•LiCl, in a 54% yield (Scheme 1b). We expected that the use of (C6F5)2AlBr [23] would render a more effective salt elimination but the corresponding LiBr complex (2•LiBr) was detected by NMR spectroscopy.…”

“…Aminoboranes (R 2 B-NR 2 ), for example, have an enormous number of researches describing their − B=N + polar double-bond character [1]. To contrast, the heavier analogues, λ 3 ,λ 3 -phosphanylalumanes (R 2 Al-PR 2 ), decrease the π-type interaction between the E and Pn atoms compared to those of aminoboranes [2][3][4] and phosphanylboranes [5,6] due to the longer E-Pn σ-bond. These aspects can afford a characteristic reactivity reflecting the adjacent but separated Lewis acids and bases, similar to the synergetic interactions of the Lewis acid and Lewis base of frustrated Lewis pairs (FLPs) toward small-molecules [7][8][9][10].…”

Synthesis and Structure of Diboraporphyrinogenes

“…Under these conditions it is not necessary to use a solvent mixture of hexane and N,N,NЈ,NЈ-tetramethylethylenediamine (tmeda) as proposed. [8,13] Due to its high reactivity 3 is prepared in situ for the synthesis of the macrocycles 5Ϫ8. Scheme 1 Reaction of 3 with iPr 2 NϪBCl 2 leads to the yellow, airand moisture-sensitive tetrathiadiboraporphyrinogene 5 in 95% yield.…”