Enaminoimine hydrochlorides

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>. 

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. 

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See also in sourсe #XX -- [ ]

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