Ethylene derivatives azomethines

Acetic anhydride Synthesis of ethylene derivs. from azomethines... 

Recently, Pelletier, Nowacki, and Mody 155) reported that treatment of alkaloid imine derivatives with ethylene oxide in acetic acid or methanol afforded the oxazolidine ring-containing alkaloids in excellent yield. Treatment of lindheimerine (7) with ethylene oxide in acetic acid afforded ovatine (6) in 98% yield. Similarly, veatchine azomethine acetate (10) afforded veat-chine acetate (210) in 97% yield. Formation of the oxazolidine ring in these... 

Unlike ethylene oxide, oxetane reacted very slowly with the alkaloid imine derivatives to afford low yields of tetrahydro-l,3-oxazine derivatives. Treatment of veatchine azomethine acetate (10) with oxetane in acetic acid at 50° afforded the six-membered carbinolamine ether, homoveatchine acetate (220), in 25% yield. The latter was isolated as a mixture of C-20 epimers. 

The same chiral auxiliary has been used in the cycloaddition of an optically active azomethine ylide to benzaldehyde and to l-nitro-2-(3,4-methylenedioxyphenyl)ethylene Ae ylide was generated in situ by treating (R)-(+)-/V-(l-phenylethyl)-A -cyanomethyl-A -trimethylsilylmethylamine (33) with silver fluoride. Unfortunately, no selectivity was observed in the first case and only a 3 2 preference was expressed in the second. Use of the azomethine ylide derived in the same manner from (/ )-(-)-N-(l-phenyl-2-methoxyethyl)-/V-cyanomethyl-N-trimethylsilylmethylamine (34) displayed a modest, but potentially useful, 4 1 diastereofacial selectivity in its reaction with l-nitro-2-(3,4-methylenedioxyphenyl)ethylene. The precise structure of the major and minor product was not determined (Scheme 25). 

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