2- Cyclohexenone boron trifluoride complex

Dienones, such as 4-[4-(trimethylsilyl)-2-butenyl]-3-vinyl-2-cyclohexenone, are useful precursors for these particular transformations the allylsilane side chain is too short for effective 1,4-addition, but just right for 1,6-addition, resulting in six-ring annulation. Three different Lewis acids can be used titanium(IV) chloride, boron trifluoride diethyl ether complex, and ethylaluminum dichloride. The best chemical yields and complete asymmetric inductions were obtained with ethylaluminum dichloride. 

A definite improvement in the synthesis of A -methoxy aziridines was achieved by substituting boron trifluoride with trimethylsilyl triflate and diethyl ether with dichloromethane"9. In this way, the A -methoxy aziridines were obtained in good yields from a variety of linear and cyclic alkenes, e.g., 6-8. For comparison, the aziridine 8 was obtained in 50% yield by using boron trifluoride- diethyl ether complex in dichloromethane. Complex product mixtures were obtained with allyl and crotyl alcohols and with cyclohexenone. Further transformation of the A -methoxy aziridines into the N-H aziridines was possible using sodium/ ammonia reduction, e.g., 9. 

Substituting lithium 2-thienylcyanocuprate for the CuCN/LiBr complex and omitting boron trifluoride etherate from the reaction of the organozinc halide species with 2-cyclohexenone indeed gave a reasonable yield (76% GC) of the... 

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