Neutral Diboron Analogues of Archetypal Aromatic Species by Spontaneous Cycloaddition

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• 作者：Dr. Merle Arrowsmith ; Julian Bö ; hnke ; Prof. Dr. Holger Braunschweig ; Dr. Mehmet Ali Celik ; Dr. Christina Claes ; Dr. William C. Ewing ; Dr. Ivo Krummenacher ; Katharina Lubitz and Dr. Christoph Schneider
• 刊名：Angewandte Chemie International Edition
• 出版年：2016
• 出版时间：September 5, 2016
• 年：2016
• 卷：55
• 期：37
• 页码：11271-11275
• 全文大小：1099K
• ISSN：1521-3773

文摘

Among the numerous routes organic chemists have developed to synthesize benzene derivatives and heteroaromatic compounds, transition-metal-catalyzed cycloaddition reactions are the most elegant. In contrast, cycloaddition reactions of heavier alkene and alkyne analogues, though limited in scope, proceed uncatalyzed. In this work we present the first spontaneous cycloaddition reactions of lighter alkene and alkyne analogues. Selective addition of unactivated alkynes to boron–boron multiple bonds under ambient conditions yielded diborocarbon equivalents of simple aromatic hydrocarbons, including the first neutral 6 π-aromatic diborabenzene compound, a 2 π-aromatic triplet biradical 1,3-diborete, and a phosphine-stabilized 2 π-homoaromatic 1,3-dihydro-1,3-diborete. DFT calculations suggest that all three compounds are aromatic and show frontier molecular orbitals matching those of the related aromatic hydrocarbons, C₆H₆ and C₄H₄²⁺, and homoaromatic C₄H₅⁺.