tert‐Amino Effect in Heterocyclic Chemistry. Synthesis of Hydrogenated Spiro Derivatives of Quinolines.

Abstract

Ring closure reactions O 0130tert-Amino Effect in Heterocyclic Chemistry. Synthesis of Hydrogenated Spiro Derivatives of Quinolines. -The synthesis of spiro derivatives of heterocycles is based on reactions proceeding by the mechanism of the "tert-amino-effect" which generalizes cyclization reactions of certain derivatives of ortho-substituted N,N-dialkylanilines. Using this strategy, a variety of spiro compounds is obtained by reaction of o-aminobenzaldehydes (III) with cyclic CH-active compounds such as (IV), (VI), (VIII), and (X). A further method involves Koevenagel condensation of (III) with malonic ester, cyclization of the resulting benzylidenemalonic esters to fused quinolines, and condensation of the latter with disubstituted urea to afford the targets. However, this method involves disadvantages associated with the formation of by-products. -(D'YACHENKO, E. V.; GLUKHAREVA, T. V.; NIKOLAENKO, E. F.; TKACHEV, A. V.; MORZHERIN*, Y. Y.; Russ.

Microwave-assisted three-component cyclocondensation of thiourea, ethyl acetoacetate, and substituted benzaldehydes

“…We investigated the three-component condensation of thiourea, ethyl acetoacetate, and p-substituted benzaldehyde derivatives in the Biginelli reaction either at the simple heating or microwave irradiation. If the reaction is carred out in the boiling ethyl alcohol using MnCl 2 ·H 2 O as a catalyst, it is completed within 6-8 h. The use of microwave irradiation makes it possible to reduce the reaction time to 150 min at 750 W. The structure of the obtained 5-(ethoxycarbonyl)-4-(4-R-phenyl)-6-methyl-3,4-di-hydropyrimidine-2(1H)-thiones I-III) was confirmed by the analytical and spectral data, which were consistent with those of the other 3,4-dihydropyrimidinethiones [1][2][3]. Thus, the behavior of the reaction components under the microwave irradiation conditions does not differ from that under the conventional heating conditions.…”

The tert-amino effect in heterocyclic chemistry: Synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives

“…[ 24 ] The application of the tert -amino effect to the synthesis of pyrido-fused benzenes, pyridazines and uracils has also been reported. [ 25 - 28 ] In this approach the ring closure occurs between the β-carbon of a vinylic group possessing electron withdrawing substituents at the β-position and the α-carbon of an ortho-tert -amino group. In a recent report this ring closure method is also extended to the preparation of new spirocyclic ring systems by incorporating the β-substituents of the vinylic group into a ring [ 29 ] in this way.…”

Interaction of 2-piperazinobenzaldehyde with cyanoacet(thio)amide: Stereoselective cyclization by the “tert-amino effect” mechanism

“…It was shown that the reaction of 2-piperazinobenzaldehyde 1 with cyanothioacetamide 2a in butanol for 2 h the product of tandem reactions [2], the Knoevenagel condensation and cyclization by the "tert-amino effect" mechanism [3-6], 2,3,4,41,5,6-hexahydro-1H-pyrazin[1,2-a]quinoline 3 was formed, while reaction of benzaldehyde 1 with cyanoacetamide 2b stopped at the stage of formation of the Knoevenagel condensation product 4b which did not cyclize on prolonged heating. When the reaction of 2-piperazinobenzaldehyde 1 with cyanothioacetamide 2a was carried out in toluene the vinyl derivative 4a was isolated, which on heating in butanol cyclized to the pyrazinoquinoline 3.…”