Improved heteroatom nucleophilic addition to electron-poor alkenes promoted by CeCl3•7H2O/NaI system supported on alumina in solvent-free conditions

被引:110
作者
Bartoli, G
Bartolacci, M
Giuliani, A
Marcantoni, E
Massaccesi, M
Torregiani, E
机构
[1] Univ Camerino, Dipartimento Sci Chim, I-62032 Camerino, MC, Italy
[2] Univ Bologna, Dipartimento Chim Organ A Mangini, I-40136 Bologna, Italy
关键词
D O I
10.1021/jo048329g
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
Conjugate addition of heteroatom nucleophiles to carbon-carbon double bonds conjugated with a strong electron-withdrawing group is one of the most important new bond-forming strategies in synthetic organic chemistry. Among the methods for these Michael additions, Lewis acids have shown the best promoter activity, and in particular, the use of reagents impregnated over inorganic supports is rapidly increased. With the increase of environmental consciousness in chemical research, the solvent-free Michael addition has attracted our attention. In continuation of our ongoing program to develop synthetic protocols utilizing cerium trichloride, we report an extension of the CeCl(3)(.)7H(2)O/NaI combination supported under solvent-free conditions to promote heteroatom Michael addition. Using neutral alumina (Al2O3) as solid support permits us to circumvent some of the problems associated with the procedure where the inorganic support is silica gel. The CeCl(3)(.)7H(2)O/NaI/Al2O3 system works well for hetero-Michael additions utilizing weakly nucleophiles such as imidazoles and carbamates, and also the reaction proceeds with good yields in the case of Michael acceptors different from alpha,beta-unsaturated carbonyl compounds. An important synthetic application of this our methodology is the intramolecular aza-Michael reaction in producing 4-piperidinone derivatives, which are of interest as synthetic intermediates toward important classes of heterocycles.
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页码:169 / 174
页数:6
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