ISSN:
0009-2940
Keywords:
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Nuclear Magnetic Resonance Studies on Boron Compounds, X: 11B, 14N, and 1H N. M. R. Studies on Boryl-substituted Thiophene, Furan, and N Methylpyrrole and Related Systems: Interaction of sp2-Boron Atoms with π-Systemδ11B data of R3-nBXn (R=alkyl; X = N(CH3)2, Cl, Br; n = 0, 1, 2) and R3-n′BXn(R = phenyl, 2- and 3-thienyl, 1-methyl-2-pyrrolyl, 2-furyl, cyclopentadienyl, vinyl, cyclopropyl; X = alkyl, N(CH3)2,Cl, Br; n = 0, 1, 2) are reported. A comparison of the two series points to increasing π-back-bonding from the ring systems to boron in the series phenyl 〈 3-thienyl 〈 2-thienyl 〈 1-methyl-2-pyrrolyl 〈 2-furyl, which is compatible with the decrease of „aromaticity“ of the cyclic systems. The influence of the conjugated double-bond system in the cyclopentadienyl group leads to a high field shift of the 11B resonance relative to that of the vinylboranes. Preparative methods for the synthesis of the five-membered heteroaromatic rings borylated in the 2-position are reported.
Notes:
Es werden die δ11B-Daten einer Reihe von Boranen des Typs R3-nBXn(R = Alkyl; X = N(CH3)2,Cl, Br; n = 0, 1, 2) und R′3-nBXn(R = Phenyl, 2- und 3-Thienyl, 1-Methyl-2-Pyrrolyl, 2-Furyl, Cyclopentadienyl, Vinyl, Cyclopropyl; X = Alkyl, N(CH3)2, Cl Br; n = 0, 1, 2)mitgeteilt. Der Vergleich beider Reihen läßt eine Zunahme der π-Rückbindung vom Ringsystem zum B-Atom in der Reihe Phenyl 〈 3-Thienyl 〈 2-Thienyl 〈 1-Methyl-2-pyrrolyl 〈 2-Furyl erkennen, die mit der Abnahme der „Aromatizität“ der Ringsysteme in Einklang Steht. Bei den Cyclopentadienylboranen führt das konjugierte Doppelbindungssystem, verglichen mit den Vinylboranen, zu einer Hochfeldverschiebung von δ11B. Präparative Methoden zur Darstellung der in 2-Stellung borylierten Heteroaromaten werden mitgeteilt.
Additional Material:
4 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19761090329
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