By Alan R. Katritzky
This quantity within the sequence summarizes the various tools 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 similar lactim ethers - finished evaluation of those hugely vital intermediates for the education of a wide selection of normal items. The e-book explains how 1,2,4-Triazolo [1,5-a] pyrimidines are of specific significance in images with different major software in prescription drugs and agrochemicals. It additionally studies tetramic acids, an importantgroup of typical items exhibiting signifcant organic task, in addition to a few chemistry.
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Extra info for Advances in Heterocyclic Chemistry, Vol. 57
Sequential treatment of those azadienes 2 with dichlorodiphenylsilane or -germanium followed by reaction of the resulting solution with DMAD at 60 or 25°C (for silicon or germanium derivatives, respectively) gave new furo[2,3-6][ 1,4]diazepines 116 and 117; either protodesilylation or protodegermylation to 118 (40-90% yield from 2) was carried out by stirring at room temperature a dichloromethane solution of trifluoroacetic acid and 116 or 117. Compounds 118 rearranged cleanly to pyridines 119 in refluxing toluene.
From 1-3 + 21 Fragments Examples of synthesis of five-membered heterocycles following this strategy are limited in number. An approach to 1,3,4-triazoles involves bonding of C-1 and C-3 of vinyl isocyanate 150 to both nitrogen atoms of aromatic hydrazines (78JOC402) (Scheme 37). The reaction was run at room temperature and gave quantitatively regioisomer 151 or a mixture of 151 and 152 when p-nitrophenyl and phenylhydrazine, respectively, were employed. 32 JOSE BARLUENGA AND MIGUEL TOMAS [Sec. - CyNC 0 M ~ Me CO2H * NaH 86 90 H 145 146 Meoy15 M e MeOH 85 % w +--) Me M e 0 Med 147 148 Me M$e Me0 149 SCHEME36 Sec.
The formation of the seven-membered ring can be rationalized by taking in mind that the conformational effects seem to favor the intermediate 115 to undergo intramolecular carbon-nitrogen bond formation between N-1 and the carbonyl function linked to C-4 (1,Sattack) (91CC353; 92MI1, 92S106). C02Me SCHEME 29 Sec. C] SYNTHESIS OF HETEROCYCLES FROM AZADIENES 27 from azadienes 2 having R2 and R3 other than hydrogen toward dimethyl acetylenedicarboxylic acid (Scheme 30). When azadienes 2 (R2 = Ph; R3 = Me) and dichlorodiphenyl silane were stirred in toluene at room temperature and then heated at 60°C with dimethyl acetylenedicarboxylic acid, eight-membered heterocycles 121 were isolated in 60-71% yield.