By Alan R. Katritzky
This quantity within the sequence summarizes the numerous equipment of the synthesis of heterocycles from azadienes with sections masking 1-azadienes, 2-azadienes, and 1,3-diazadienes. It covers the piperazine-2,5-diones and comparable lactim ethers - complete overview of those hugely vital intermediates for the coaching of a wide selection of usual items. The ebook explains how 1,2,4-Triazolo [1,5-a] pyrimidines are of specific value in images with different major program in prescribed drugs and agrochemicals. It additionally experiences tetramic acids, an importantgroup of usual items exhibiting signifcant organic job, in addition to a few chemistry.
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Additional resources for Advances in Heterocyclic Chemistry, Vol. 57
B R3 R4 I 0 H 108 107 NHR' R4 A N 'H 2 LDA N-SO2 H/ - R"H2 109 I H 110 SCHEME 27 with enolates of substituted acetates gives rise to mixtures of 2-pyridones and isomeric dihydro-Zpyridones (8 1TL3769). The [4 + 21 cycloaddition of benzo-1-azadienes with electrophilic carbon-carbon double bonds has been implemented by de Meijere and coworkers (90CC574); in this case, the authors used N-unsubstituted benzophenone imine and cyclopropylideneacetates, and the reaction represents a new isoquinoline ring synthesis.
COMe, CH=CHz. - [O] I H 255 (Y = CH=CH) 256 (Y = 0, S; RZ = H) SCHEME 57 of iminophosphorane 260 and diphenylketene and cycloadded to a second molecule of diphenylketene to furnish 1,3-oxazine derivative 262 in 60% yield [89JCS(P1)2140]; in addition, the [4 + 21 cycloaddition reaction of 261 with aryl isocyanates and diary1 thioketones has just been reported (92LA 15). Isolated examples of intramolecular [4 + 21 cycloaddition reac- 52 JOSE BARLUENGA AND MIGUEL TOMAS [Sec. 8 I R2 257 Ph ph2C=C=o * 9 Ph Ph2C=C=O '**yPh 261 Ph * # Ph 'k: Ph 262 SCHEME 58 tions involving the 2-azadiene unit of a ketenimine have been published (91TL5379; 92JOC929).
Recently, Japanese workers [90TL(31)3753] described a simple approach to this type of N-acyl- I-azadiene system by means of trimethylsilylaldimines derived from a,gunsaturated aldehydes (Scheme 22). Taking advantage of the chemistry of silylimines, aldehydes 85 were easily converted into 1-azadiene species 86, which were heated to furnish e m 87 and/or endo 88 cycloadducts in 30-65% overall yield from 85. They observed that the formation of quinolizinones ( X = CH,-CH,) occurs exclusively via an exo transition state leading to 87, whereas in the case of indolizinones ( X = CH,) and their oxa derivatives (X = 0) the endo isomers 88 predominate.