The term "tert-amino effect" was proposed in 1972 [1] for the cyclization reactions of tertiary anilines containing various double bonds at the ortho position. Meth-Cohn and Suschitzky [1] referred to the first observation of the tert-amino effect by Pinnow in 1895 [2]. Many different examples of reactions involving the tert-amino effect have now accumulated, and it clearly is a convenient method for the synthesis of an impressive number of nitrogen-containing heterocycles that otherwise might be difficult to obtain. Reviews were published by Reinhoudt in 1990 [3] and by Meth-Cohn in 1996 [4] on heterocyclization reactions that take place by the mechanism of the tert-amino effect. Another review dedicated to 1,6-and 1,8-naphthiridine derivatives was published in 2003 by Quintela [5]. In the review [6] that we published in 2005, attention was focused on the use of such reactions for the synthesis of spiro compounds. In the review [7], published in 2006, the cyclization reactions of ortho-vinylanilines and their heterocyclic aza analogs were considered, and classification according to the method of ring formation was proposed.

Cyclization of 2 (4 R piperidino)benzaldehydes with 5 methyl 2 phenyl 2,4 dihydro 3H pyrazol 3 one proceeding via tert amino effect mechanism is stereoselective. Relative configu ration of (3R*,4aS*,5R*) 2,3,4,4a,5,6 hexahydro 1H benzo[c]quinolizine was established on the base of NMR spectroscopy data and X ray analysis.

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Review: 112 refs.

Synthesis and Kinetics of the Cyclization of 3-(Dialkylaminophenyl)-2-(phenylcarbonyl)-prop-2-enenitriles. -Reaction of o-pyridazinobenzaldehydes (I) with benzoylacetone affords fused tetrahydroquinoline derivatives (IV) in a diastereoselective fashion via intermediate propenenitriles (III). Similar reaction of benzaldehydes (V) stops at the formation of the Knoevenagel condensation products, i.e. propenenitriles (VI), due to the lower basicity of the piperazine and morpholine fragment, respectively. -(PLATONOVA*, A. Y.; GLUKHAREVA, T. V.; ZIMOVETS, O. A.; EL'TSOV, O. S.; MORZHERIN, Y. Y.; Chem. Heterocycl. Compd. (N. Y., NY, U. S.) 49 (2013) 5, 736-745, http://dx.

The considerable interest in tetrahydroquinolines and their derivatives is primarily due to the biological activity of tetrahydroquinolines themselves [1,2], as well as their remarkable reactivity and the variety of chemical transformations, which make these compounds convenient building blocks in the synthesis of other structures with high biological activity [3]. One method for the synthesis of tetrahydroquinoline systems is the cyclization of N,N-dialkyl-o-vinylanilines proceeding through a tert-amino effect mechanism [4][5][6][7].We studied the reaction of 2-dialkylaminobenzaldehydes 1a-i with benzoylacetonitrile (2), leading to N,N-dialkyl-o-vinylanilines 3a-i, which, in turn, cyclized to the condensed 1,2,3,4-tetrahydroquinolino-5-carbonitriles 4a-i. Examination of the literature showed that an analogous reaction has been carried out only using o-piperidinobenzaldehyde as the starting reagent [8].Knoevenagel condensation products 3a-e,h,i could not be isolated in the condensation of 2-piperidinobenzaldehydes 1a-e,h,i, since the cyclization to give 1,2,3,4-tetrahydroquinolino-5-carbonitriles 4a-e,h,i dominated under these reaction conditions [9]. Knoevenagel condensation products 3f,g, that did not undergo cyclization in toluene, were isolated only in the case of benzaldehydes 1f,g. This finding may be attributed to the lower basicity of the morpholine and piperazine dialkylamino groups. 1,2,3,4-Tetrahydroquinolino-5-carbonitriles 4f,g were obtained by the cyclization of N,N-dialkyl-o-vinylanilines 3f,g upon heating in 1-butanol at reflux. 1,2,3,4-Tetrahydroquinolino-5-carbonitriles 4a-i contain from two to four asymmetric sites.