Download Advances in Heterocyclic Chemistry, Vol. 26 by A.R. Katritzky, A.J. Boulton (Eds.) PDF

By A.R. Katritzky, A.J. Boulton (Eds.)

(from preface)Volume 26 includes 3 chapters. C.A.Ramsden reports heterocy-clic betaines derived from 6-membered heteroaromatic jewelry. those compounds were intensively studied over the last 10 years and feature no longer formerly been comprehensively reviewed. O. Meth-Cohn and B. Tarnowski summarize the chemistry of the thiocoumarins, a a little ignored crew of heterocycles. ultimately, W. Friedrichsen has reviewed the chemistry of the benzo[r]furans which, in contrast to the aza and thia analogs, haven't formerly been thought of during this sequence. the following back we've got a gaggle of compounds the chemistry of which has complex significantly during the last decade.

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Chem. 37, 1592 (1972). 17' I" Sec. B] 49 HETEROCYCLIC BETAINES 14. I ,2,3-Benzotriazinium-4-aminides (269) NR' NHAr NHAr Menschutkin alkylation of 4-arylamino- 1,2,3-benzotriazines (270) in ethanol occurs at the 2-position. The benzotriazinium iodides (271) so formed are readily deprotonated by base giving the betaines (269; R' = alkyl, R2= aryl). In the presence of sodium ethoxide, alkylation of benzotriazines 270 occurs at positions 2 and 3. The bright red betaines 269 form salts with dilute hydrochloric acid and are dealkylated by hot ethanolic potassium hydroxide.

Perkin 2, 1304 (1977). Sec. A] 25 HETEROCYCLIC BETAINES 4. Thiopyryliun~-3-olates (132) m& R R R R 8 (135) exo-syn (136) endo-syn Thiopyran-3(6H)-ones (133; R = H or Me) are converted into 3hydroxythiopyrylium perchlorates (134; R = H or Me) by triphenylmethyl perchlorate. Deprotonation of these salts (134) by tertiary base did not liberate the thiopyrylium-3-dates (132) but instead gave dimeric products (135 and 136) in high yield. Evidence for the transient formation of the mesomeric betaines (132) is provided by the appearance of a greenishyellow coloration which rapidly fades.

2. 217 3. 4-(Pyridinium)phenolates(297) These compounds (297) have interesting thermochromic and solvatochromic effects. ''' Dramatic changes are also observed when the solvent polarity is 'lo ''I *'' 'I3 'I4 '15 'Ih 'I' W. Schneider, W. Dijhling. and R. Cordua. Bcr. rch. Chrrn. Ges. B 70. 1645 (1937). K. Dimroth. C. Reichardt, and A. Schweig, Jusrus Liehigs Ann. Chenz. 669, 95 (1963). G . Doleschall and K. Lempert, Tetraliedron 29, 639 (1973). G . Doleschall and K. Lempert, Tetraliedron 32, 1735 (1976).

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