关键词: 铬, 去芳构化, 烯丙基化, 羰基化, η⁶-配位

The rapid and selective assembly of complex and high-value structures from fundamental starting materials remains one of the most important goals in organic chemistry. The carbonylative 1,2-difunctionalization of olefins is of great attraction since it can simultaneously install a synthetically significant carbonyl group and another functional group across C=C double bonds, providing a straightforward and efficient method for the formation of high-value β-functionalized carbonyl compounds. Compared with alkenes, dearomative carbonylative 1,2-difunctionalization of arenes is much less studied even though this reaction would not only introduce two important functional groups but also convert flat arenes into three-dimensional architectures of increasing interest in medicinal chemistry. The big challenges of this reaction arise from breaking aromatic resonance stabilization and selectivity issues. Herein, we describe a novel dearomative 1,2-allylation/aminocarbonylation of chromium-bound arenes, which enabled rapid and selective incorporation of an allyl group and an amide group into arene π-systems to produce a wide range of β-allylated amide compounds containing 1,3-cyclohexadiene rings. The η⁶-coordination using Cr(CO)₃ unit not only activated the inert benzene π-bond towards dearomatization but also offered the CO source for the carbonylation process. The synthetic potential and the practicability of this method were well demonstrated by the CO-gas-free reaction conditions, the broad substrate scope, and the excellent functional group tolerance. A general procedure for this dearomative 1,2-allylation/aminocarbonylation reaction is depicted as follows: under N₂ atmosphere, allyltrimethylsilane (0.40 mmol, 2.0 equiv.) was slowly added to a solution of (η⁶-arene)Cr(CO)₃ (0.20 mmol, 1.0 equiv.) and Me₄NF (0.60 mmol, 3.0 equiv.) in tetrahydrofuran (THF) (2.0 mL) at 0 ℃. The reaction mixture was stirred at 0 ℃ for 4 h, then cooled to －45 ℃, followed by the addition of N-chloroamine (0.80 mmol, 4.0 equiv.). The reaction mixture was allowed to warm to 30 ℃ gradually within 20 min and stirred at 30 ℃ for another 10 h. The solvent was evaporated in vacuo and the crude mixture was purified by preparative thin-layer chromatography (TLC) to yield the corresponding dearomative allylation/aminocarbonylation product.

Key words: chromium, dearomatization, allylation, carbonylation, η⁶-coordination