Synthesis of 1,3-Oxazines and Furo[2,3-b]pyrans by reaction of 2-amino-4,5-dihydro-3-furancarbonitriles with dibenzoyldiazomethanes
摘要:
2-Amino-4,5-dihydro-3-furancarbonitriles (1) react with a slight excess of dibenzoyldiazomethane in the presence of rhodium(II) acetate to give 1,3-oxazin-4-ones (2). With three equivalents of dibenzoyldiazomethane compounds 1 react to afford furo[2,3-b]pyran-3a-carbonitriles (3). Compound 3a was also obtained by treatment of 2a with two equivalents of dibenzoyldiazomethane.
An efficient Diels-Alder reaction is described in the furan series, leading to phthalimides in high yields. Thermal treatment of 2-(4-morpholinyl, 1-piperidinyl, and 1-pyrrolidinyl)-3-furancarbortitfiles with maleimide derivatives, e.g. maleimide, N-methylmaleimide, N-benzylmaleimide, N-phenylmaleimide and N-(4-nitrophenyl)maleimide, in boiling acetic acid caused a [4 + 2] cycloaddition reaction to give the corresponding phthalimide derivatives.
Synthesis of Dihydrooxepins by the Cycloaddition of 2-Amino-4,5-dihydro-3-furancarbonitriles with Dimethyl Acetylenedicarboxylate
A facile and efficient synthesis of dihydrooxepins is described. Treatment of readily available 2-amino-4,5-dihydro-3-furancarbonitriles with dimethyl acetylenedicarboxylate at room temperature caused smoothly a cycloaddition reaction, followed by a ring expansion, giving the corresponding dihydrooxepin derivatives.