No abstract

The term "tert-amino effect" was proposed by Meth-Cohn and Suschitzky [1] for the general reaction of cyclization of some derivatives of ortho-substituted N,N-dialkylanilines. The cyclization which occurs at the unsaturated α-carbon atom of the dialkylamino group, was described for compounds with an unsaturated (A=B) ortho substituent, including at least one heteroatom (nitroso-, azo-, azomethino-, nitro-, amino-, or carbonyl functions) [2]. Professor Reinhoudt's group established that cyclization also took place with N,N-dialkylanilines with a vinyl substituent in the ortho position [3]. This reaction is an original method for the formation of a C-C bond with an unactivated NCH 2 group [4].We have shown previously [5][6][7][8] that the Knoevenagel condensation occurs in tandem with cyclization via the tert-amino effect mechanism when 2-dialkylaminobenzaldehydes react with cyclic CH-active compounds (derivatives of 1,3-cyclohexandione, Meldrum's acid, barbituric acid) [9]. These reactions were shown to occur stereoselectively [4, 10-12].The aim of the current work was to investigate the reaction of 2-piperidinobenzaldehydes 1a-d with 2-aryl-5-methyl-2,4-dihydropyrazol-3-ones 2a-c. The reactions were carried out in boiling butanol. 3'-Methyl-1 '-phenyl-2,3,4,4a,5,6-hexahydro-6H-spiro[benzo[c]quinolizine-5,4'-pyrazol]-5'-ones 3a-j (Table 1) were formed as a result. The reaction products contain two asymmetric centers, so it is consequently possible to form two diastereoisomers. It was shown that the reaction proceeded stereoselectively and led predominantly to a single diastereomer (up to 95-98%).In the 1 H NMR spectrum of the basic reaction product ( Table 2) the signal of the proton on the carbon atom 4a appears as a doublet of doublets in the 3.13-3.18 ppm region. This proton interacts with a large coupling constant of 11.2-11.5 Hz with the axial hydrogen in position 4 and with a small coupling constant of 2.3-2.5 Hz with the equatorial hydrogen in the same position. Hence the hydrogen in position 4a occupies an axial position.

Nucleophilic substitution in 5-halo-1,2,3-thiadiazoles is a convenient method for the synthesis of various heterocycles [1,2]. We have previously shown that such reactions may be accompanied by rearrangement of the thiadiazole ring and reactions at C(4) of the ring [3,4]. In a continuation of our studies, we have developed a simple preparative method for the synthesis of a previously unreported heterocyclic system, namely, [1,2,3]thiadiazolo[5,4-e][1,4]oxazepine by the reaction of the ethyl ester of 5-chloro-1,2,3-thiadiazole-5-carboxylic acid (1) [5] with diethanolamine. This reaction involves nucleophilic substitution of the chlorine atom followed by intramolecular transesterification to give heterocycle 2. In contrast to the reaction indicated above, the reaction of thiadiazole 1 with monoethanolamine leads to the Dimroth rearrangement product [6], 5-mercapto-1,2,3-triazole 3, which reacts with starting 5-chloro-1,2,3-triazole 1 under the reaction conditions to give sulfide 4.

benzo[c]quinolizine-5,4'-pyrazol]-5'-ones. -The synthesis of the title compounds (V) (10 examples) is achieved by reaction of 2-piperidinobenzaldehydes with dihydropyrazolone (IV) via the "tert-amino effect" mechanism and proceeds stereoselectively to give a single diastereomer. -(GLUKHAREVA, T. V.; KROPOTINA, P. E.; KOSTERINA, M. F.; NEIN, Y. I.; DEEVA, E. V.; MORZHERIN, Y. Y.; Chem. Heterocycl. Compd. (N. Y.) 43 (2007) 1, 76-81; Urals State Tech. Univ., Ekaterinburg 620002, Russia; Eng.) -H. Toeppel 46-123

Synthesis of 5,6-Dihydro[1,2,3]thiadiazolo[5,4-e][1,4]oxazepin-8(4)-one. -A simple method for the synthesis of the previously unreported heterocyclic system (III) is developed. -(KROPOTINA, P. E.; GLUKHAREVA, T. V.; ISAKOVA, I. S.; ALEKSEEVA, E. A.; MORZHERIN*, Y. Y.; Chem. Heterocycl. Compd. (N. Y.) 44 (2008) 2, 233-234; Urals State Tech. Univ., Ekaterinburg 620002, Russia; Eng.) -C. Cyrus