Pyrimidines fused tricyclic

Monocyclic imino-ketenimines, in which the reactive functionalities are linked by an allylic or vinylic tether connecting the imino and ketenimino nitrogen atoms, undergo a formal intramolecular [2+2] cycloaddition to yield fused tricyclic 2-iminoazetidines, namely, azeto[l,2-a][l,3]thiazolo[4,5-rf] [pyrimidines 10 <02EJO4222>, and azeto[l,2-... 

Lactonization of hydroxy acids 8 (Ar = 2-OHCeH4, = H, X = O) to fused tricyclic benzopyrano[4,3-d]-pyrimidines 288 (Z = O) was achieved using 2 equiv of TBTU and 4 equiv of DIPEA in dichloromethane (Method A, Scheme 112) (09T5949). Moreover, 288 (Z = NH) was obtained from 8 (Ar = 2-CIC6H4 = Et X = O, S) through cyclization with ammonia on... 

A novel tricyclic piperidine-fused pyrazolo[l,5-a]pyrimidin-7-(4//)-one has been synthesized with regioselective formation of the tricyclic core structure <06MI715>. 

Pyrimidine annulated heterocycles fused at positions 5 and 6 to uracil were synthesized via a three-step sequence starting from uracil 63 [20]. Firstly, the reaction with 3-bromocyclohexene gave the AT-allyl-vinyl core system 64 in 80% yield. Upon heating 64 in EtOH in the presence of HCl, aza-Claisen rearrangement gave rise to the C-cyclohexenyl uracil 65 in 38% yield. Final bromination ( 66) and dehydrogenation steps ( 67) allowed synthesis of the desired tricyclic fused uracil systems (Scheme 15). 

Tricyclic-fused pyrimidines containing sulfur atoms are accessible from various uracil derivatives. 10-Thiaisoalloxazines are synthesized starting from 6-(o-amino-phenylthio)uracils after diazotization, azide exchange,... 

Two groups of polycyclic heterocycles are treated the 8-azapurines by A. Albert and tricyclic fused-pyrimidines by I. Hermecz and L. Vasvari-Debreczy. 

The confusion that can arise when the formula of a relatively simple fused heterocycle is wrongly drawn may be illustrated with a tricyclic compound which may be drawn in several ways, some of which are shown in (1,8) to (1.12). None of these is in accord with lUPAC recommendations (1.13) is the correct formula and is the one that should be used. Peripheral numbering of this compound is shown and its name is pyrazinol2, 3 4.5]thieno[3,2-[Pg.21]

An additional heterocyclic ring fused to a (6 5 6) system can be constructed by a cyclocondensation reaction of an appropriately substituted tricyclic derivative with an external reagent. The NH2-CN functionality of (177) was transformed into a pyrimidine by the reaction with formamide <91H(32)895>, and cyclocondensation of the Ac-OH functionality in (178) with phenyl-hydrazine gave a pyrazole <9lH(32)90l>. A hydrazino derivative (179) was condensed with a carboxylic acid to give a 1,2,4-triazole in the reaction that involves an N-2 atom of (179) <88Ci(L)785>. 

The Wittig-type reactions of iminophosphoranes with isocyanates and related compounds have also been extensively used in heterocyclic synthesis. Examples include the preparations of the mesoionic [l,3,4]thiadiazolo[2,3-c][l,2,4]triazines (210) from (209), 0 bicyclic guanidines, e.g. (212), from (211), naphthypyridines (215), (216), and (217) from (213) and (214), 2 pyrido[l,2-f]pyrimido-[4,5-d)pyrimidines (218), 7H-pyrido-[4,3-c]- (219) and 10H-pyrido[3,4-b]- (220) carbazoles, tricyclic fused 2,4-diimino-l,3-diazetidines (222) from the bisiminophosphorane (221), benzotriazepines (225) from (223) and (224), 6 and mesoionic thiazolo-[2,3-b]-1,3,4-thiadiazoles (227) and N,N-bisheteroarylamines from the iminophosphorane (226), derived from 3-amino-4-phenylthiazole-2(3H)-thione. The carbodiimides (229), prepared from the iminophosphorane (228), can be converted into quinolines or a-carboline derivatives depending on the nature of the isocyanate used in the reaction with (228) and the reactions of iminophosphoranes (230) and (231) with aryl and styryl isocyanates provide one-pot syntheses of quinoline, a-carboline, and quinindoline derivatives. 9... 

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