Studies on the Reaction of Quinazoline with Aromatic Aldehyde in the Presence of Cyanide Ion. I. The Extension of the Benzoin Condensation

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The possible reaction process for the formation of 4, 4'-biquinazoline (II) obtained from the reaction of quinazoline (I) with cyanide ion were discussed and proposed by the scheme shown in Chart 1, which involved benzoin type condensation and oxidation, in successive step. When the mixture of I and aromatic aldehyde treated with cyanide ion, aryl 4-quinazolinyl ketone (IX) was obtained together with II, even if both of the yields were poor. Typically, in the case of o-anisaldehyde and m-chlorobenzaldehyde, 2-methoxyphenyl 4-quinazolinyl ketone (IX-2), 3-chlorophenyl 4-quinazolinyl ketone (IX-6) and α-(2-methoxyphenyl)-4-quinazolinemethanol (VII-2), α-(3-chlorophenyl)-4-quinazolinemethanol (VII-6) were respectively obtained together with II. The reaction with benzaldehydes which was substituted with strongly electron donating (such as dimethylamino and hydroxyl group) or strongly electron attracting group (such as nitro and cyano group) did not give any of the corresponding IX. Especially, in the case of nitrobenzaldehyde, the corresponding dimethyl azodibenzoate (XV) and dimethyl azoxydibenzoate (XVI) were obtained. Although there were the two possible reaction process for the formation of IX, path A and B, which were similar to that of cross benzoin condensation and oxidation in successive step, it might be considered that this cross benzoin type condensation might proceed by path A rather than path B.