Intramolecular C–F and C–H bond cleavage promoted by butadienyl heavy Grignard reagents

• Published in: Nature communications 2014-07, Vol.5 (1), p.4508-10, Article 4508
• Main Authors: Li, Heng, Wang, Xiao-Ye, Wei, Baosheng, Xu, Ling, Zhang, Wen-Xiong, Pei, Jian, Xi, Zhenfeng
• Format: Article
• Language: English
• Subjects: 140/131; 639/638/403/934; 639/638/406; Alkaline earth metals; Barium; Calcium; Cleavage; Derivatives; Heavy metals; Humanities and Social Sciences; Hydrogen bonds; Laboratories; Metals; multidisciplinary; Naphthalene; Organic chemistry; Organomagnesium compounds; Perfluoro compounds; Reagents; Science; Strontium
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms5508

Organomagnesium compounds (Grignard reagents) are among the most useful organometallic reagents and have greatly accelerated the advancement of synthetic chemistry and related sciences. Nevertheless, heavy Grignard reagents based on the metals calcium, strontium or barium are not widely used, mainly due to their rather inert heavy alkaline-earth metals and extremely high reactivity of their corresponding Grignard-type reagents. Here we report the generation and reaction chemistry of butadienyl heavy Grignard reagents whose extremely high reactivity is successfully tamed. Facile synthesis of perfluoro-π-extended pentalene and naphthalene derivatives is realized by the in situ generated heavy Grignard reagents via intramolecular C–F/C–H bond cleavage. These obtained perfluorodibenzopentalene and perfluorodinaphthopentalene derivatives show low-lying LUMO levels, with one being the lowest value so far among all pentalene derivatives. Our results set an exciting example for the meaningful synthetic application of heavy Grignard reagents. Grignard reagents are one of the mainstays of organic synthesis, but analogues with other Group 2 metals (heavy Grignards) are less easy to control. Here, the authors generate butadienyl calcium and barium heavy Grignards and control their reactivity in C–F and C–H cleavage reactions.