Syntheses, structures, and reactivity of 2,5-diboryl-1-alkylpyrroles and di(1-alkyl-2-pyrrolyl)boranes

Reactions of 2,5-dilithiated 1-methylpyrrole (1a) with CIB(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)borane s 3e and 3f, respectively. NMR and MS data are in agreement with the compos itions of the compounds, which are confirmed by X-ray structure analyses fo r 2a, 2b, 2d, und 3e.