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2.5- Cyclohexadienone hydrazones

Synthesis of [1,2,3]triazolo[1,5-c]pyrimidines and [1,2,4]triazolo[1,5-c]pyrimidines A novel approach to [l,2,3]triazolo[l,5-c]pyrimidines is shown in Scheme 55. Batori and Messmer - in the course of their investigations on fused azolium salts - described a synthetic pathway to l,3-disubstituted[l,2,3]triazolo[l,5-c]-pyrimidinium salts <1994JHC1041>. The cyclization was accomplished by transformation of the hydrazone 436. This compound was subjected to an oxidative ring closure by 2,4,4,6-tetrabromo-2,5-cyclohexadienone to give the bicyclic quaternary salt 437 in acceptable yield. [Pg.733]

An unusual one-pot intramolecular sulfoxide alkylation-elimination reaction was found by Gibson et al. <2001SL712>. These authors found that treatment of 459 with potassium bis-trimethylsilylamide resulted in a ring closure to 460 in acceptable yield. Furthermore, Batori and Messmer found an effective method for preparation of [l,2,3]triazolo[l,5- ]pyrimidinium salts <1994JHC1041> oxidative cyclization of hydrazones 461 by 2,4,4,6-tetrabromo-2,5-cyclohexadienone gave rise to the quaternary salts 462. Under certain reaction conditions, the formation of 6-bromo-salts 462 (R6 = Br) was also experienced. As neither the starting compound nor the quaternary triazolopyridinium salt underwent bromination in this position, the authors assumed that this bromination process occurred on one of the intermediates in the course of the above-mentioned cyclization reaction. [Pg.739]

Carbena-cyclohexadienone (3). Photolysis or thermolysis of -quinone diazides (15) easily led to 3. The precursors of 3 are either />-aminophenols (14), -quinones (77) or anthrones (76). Diazotization of 14, Bamford-Stevens reaction of the tosyl-hydrazone of 77, or diazo-group transfer to 76 afforded the corresponding -quinonediazides 15 31-84)... [Pg.114]

A/ AT -diphenylhydrazone was discovered by using a computer-assisted synthetic design program.Sodium hydroxide converts the cyclohexadienone phenyl-hydrazone (394) into the indazole (395), possibly by way of the intermediate shown in Scheme 5. ... [Pg.180]


See other pages where 2.5- Cyclohexadienone hydrazones is mentioned: [Pg.183]    [Pg.249]    [Pg.183]    [Pg.249]    [Pg.726]   


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2,4-cyclohexadienone

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