The reaction of 1‐(hydrazidomethyl)‐6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline 3 with aromatic aldehydes yield hydrazones 4a,b or pyrimido[6,1‐a]isoquinolines 5a‐c depending upon the proportions of the reagents. With ketones, 3 gives only hydrazones 4a‐d and 7, which can be transformed to pyrimidoisoquinolines 10a‐e and 11 with aldehydes. The ring closures are stereospecific; the relative configurations were determined by DNOE measurements.

A number of 2‐hydroxycycloalkyl‐substituted 1,3,4‐oxadiazole, 1,3,4‐thiadiazole and 1,2,4‐triazole derivatives were prepared by different methods from cis‐ and trans‐2‐hydroxy‐1‐cycloalkanecarbohydrazides and their isocyanate or isothiocyanate adducts. In contrast with the related ring‐closure reactions of 2‐aminobenzoylhydrazides, no condensed skeleton heterocycles were formed in this case.

The reaction of the readily available hydrazide (I) with aldehydes (II) yields hydrazones (III) or heterotricycles (IV) depending upon the proportions of the reagents used.

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ChemInform Abstract 1-Hydrazinomethyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (I) reacts with equimolar amounts of the aromatic aldehydes (II) to give the hydrazones (III). With an excess of (II), a stereospecific ring closure reaction leading to the formation of the pyrimido(6,1-a)isoquinolines (IV) is observed.