Heterocycles with a bridging nitrogen atom. 19. Development of routes for the synthesis of oxazoloisoquinolinium salts based on phenacylation of α-methyl-1(3)-isoquinolones

Abstract

Alkylation of 3-methyl-1-isoquinolone and 1-methyl-3-isoquinolone with phenacyl bromides proceeds regioselectively with the formation in the first case of only an N-phenacyl derivative and in the second only the O-derivative. The 5-methyl[1,3]oxazolo[3,2-a]isoquinolinium salt has been synthesized and itsreactions with ammonia, morpholine, and sodium methylate have been investigated.

Pyrroles from oxazoles

“…Such a transformation proceeds successfully under the action of secondary amines [38][39][40][41][42][43] or alcoholates [42,44] and is accelerated by microwave irradiation [43]. The functions in the pyridine fragment vary extremely widely, and they include acceptor type substituents (A = CN, CONH 2 , CO 2 Et, NO 2 ), alkyl groups and/or alicycles where the number of additional methylene units n varies from 1 to 4 [42][43][44][45][46][47][48]. The preparative aspects of this reaction were described in the review [38], and in this context it is important to note the uniqueness of the structural type of this oxazoles to pyrroles conversion, which does not have analogs in the chemistry of monocyclic oxazolium salts.…”