Enaminoimine

A diastereoselective synthesis of bis(3,5)pyrazolophanes was accomplished by sequential inter- and intramolecular cycloadditions of homochiral nitrilimine intermediates . A-Alkyl pyrazolidine-3,5-diones were synthesized in a three-step sequence from dialkyl malonates <00JHC1209>. Methyl acetoacetate was employed as the initial substrate to 3-carboxamido-4-pyrazolecatboxylic acid derivatives <00JHC175>. Vilsmeier type reagent 33 reacted with imines 34 to afford enaminoimine hydrochlorides 35, which were transformed to pyrazoles 36 upon addition of hydrazine <0OJHC13O9>. 

Formal substitution of the carbonyl group of enaminones by an imino group leads to enamino imines. In the reaction with isocyanates or isothiocyanates they result in urea or thiourea derivatives, which can be transformed to pyrimidines or pyrimidones depending on substitution340 (equation 258). Treatment of similar enaminoimines with hydroxylamine gives regiospecifically isoxazoles by thermal cyclocondensation of the isolated oximes341 (equation 259). 

The reduction of a series of 1,3-diimines (76) has been investigated in which the dissolving metal reductions have been carried out both in the presence and absence of proton donors. These compounds exist as a tautomeric mixture of two enaminoimines (77) and (78) and the diimine (76). Reduction by Na-propan-2-ol of five examples (Ar = Ph, 3-tolyl R = Me R = Ph, p-tolyl, cyclohexyl) gave excellent (90-99%) yields of diastereomeric mixtures of three of the four possible fully reduced diamines in which no isomer comprised more than 50% of the reaction mixture. Diamines (79) were not observed, and their absence was attributed to steric factors. On reduction with Li-THF for several hours, followed by quenching with methanol, ethanol or water a number of these tautomeric mixtures (76, Ar = Ph, 3-tolyl R = H, Me, PhCH2, CH2==CH—CH2 R = Ph, 3-tolyl, Me, cyclohexyl) gave saturated ketones, (80) in 70 to 93% yield. ... 

Vilsmeier-type reagent 749 reacted with imines 750 to afford enaminoimine hydrochlorides 751, which were transformed to pyrazoles 752 upon addition of hydrazine (Scheme 94) <2000JHC1309>. A variety of vinylogous iminium salts 753 were useful precursors for the regiocontrolled synthesis of heterocyclic appended pyrazoles 754 (Equation 161) <2002T5467>. 

The short and convenient synthesis of novel naphthopyranoquinolines from naphthopyran chloroaldehydes via the Doebner-Miller synthesis was developed in the laboratory of J.K. Ray. The chloroaldehydes were treated with 2.5 equivalents of a substituted aniline in ethanol in the presence of 2N HCI to afford enaminoimine hydrochlorides in good yield. These hydrochloride salts were exposed to heat at a temperature slightly above their melting point, resulting in ring-closure and elimination of one equivalent of arylamine hydrochloride. 

According to Barluenga and coworkers enaminoimines react with acetylenedi-... 

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