Fine-Tunable 3,4-Dihydroquinazol-2-ylidene Carbenes: Synthesis, Rhodium(I) Complexes, and Reactivity

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• 作者：Jun Zhang ; Xinke Qin ; Jun Fu ; Xiao Wang ; Xiaolong Su ; Fangle Hu ; Jiajun Jiao ; Min Shi
• 刊名：Organometallics
• 出版年：2012
• 出版时间：December 10, 2012
• 年：2012
• 卷：31
• 期：23
• 页码：8275-8282
• 全文大小：427K
• 年卷期：v.31,no.23(December 10, 2012)
• ISSN：1520-6041

文摘

The design and synthesis of various new six-membered cyclic formamidinium salts with a 3,4-dihydroquinazoline core have been reported in this paper. Our synthetic strategy allows access to a kind of tailor-made 3,4-dihydroquinazolinium salts bearing different substituent combinations. A series of novel 3,4-dihydroquinazolin-2-ylidene-based rhodium(I) complexes were prepared by the reaction of [Rh(cod)Cl]₂ with the free carbene obtained in situ from the deprotonation of the corresponding 3,4-dihydroquinazolinium salts with KN(SiMe₃)₂. The NHCs prepared in situ can also react with S₈ or CS₂ to afford the corresponding thiones or NHC鈥揅S₂ adducts, respectively. The rhodium(I) complexes were transformed to the corresponding dicarbonyl complexes, and the 谓(CO) values of the corresponding dicarbonyl Rh complexes indicate the 3,4-dihydroquinazol-2-ylidenes are stronger electron donors than normal five-membered NHCs. The Rh complexes are highly active in the arylation of carbonyl compounds, and the 3,4-dihydroquinazolin-2-ylidenes prepared in situ upon deprotonation are powerful in palladium-catalyzed Suzuki cross-coupling reactions at room temperature with a ppm scale catalyst loading with TONs of up to 425鈥?00.