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[摘要]：A procedure for the synthesis of 4.5-dihydroisoxazoles by condensation of primary nitro compds. with olefins by using a copper/base catalytic system is described. The catalytic effect of copper(II) salts is evidenced by comparison of the reaction rates. Thus, activated nitro compds. react faster than with org. catalysis by tertiary amines, whereas nitroalkanes, unable to condense with dipolarophiles in the presence of the base alone, undergo the reaction on addn. of a copper(II) catalyst. The obsd. occurrence of induction periods in most reactions is ascribed to an equil. preceding the rate-detg. step, and gives a hint as to the proposed reaction mechanism. The results indicate that this method might be of practical and general utility for synthetic practice. |
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