Ring-Closure Reactions of ortho-Vinyl-tert-anilines and (Di)Aza-Heterocyclic Analogues via the tert-Amino Effect: Recent Developments

Abstract

One version of the tert-amino effect operating in tertanilines possessing an ortho-vinyl substituent affords a fused tetrahydropyridine ring by an isomerization process with the formation of a new carbon-carbon bond between the vinyl and tert-amino moieties. Since its discovery in 1984, this type of cyclization has been efficiently used for the construction of fused-ring systems. However, it has been found that the electron-deficient heterocyclic analogues of tert-anilines, such as diazines, may undergo isomerization at considerably lower reaction rates and, as a consequence, their reactions may require harsh conditions. Recent synthetic studies have indicated that the rate and yield may be improved by incorporating the b-vinylic carbon atom into an electron-deficient ring and/or buttressing the tert-amino group, and/or performing the reaction by means of microwave irradiation.This review describes relatively recent synthetic transformations involving this type of tert-amino effect and devotes special attention to structure-reactivity relationships including regio-and stereochemical aspects.

Regioselective reaction of ortho-piperidinobenzaldehydes with pyrazolone

“…All signals for the aliphatic protons are assigned by 2D 1 H-1 H COSY, 1 H-1 H NOESY and 1 H- 13 C HSQC (for compound 3d) and 1 H- 13 C HMBC experiments (for compounds 3a,d). The most informative cross peaks in the 2D 1 H- 13 2), H(4 ax ) and H(4 eq )/C(3), H(4 ax ) and H(4 eq )/C(4a), H(4 ax )/C (5). It should be noted that in the spectrum, no cross peak H(4 eq )/C(5) was observed, due probably to the fact that according to X ray diffraction data the dihedral angle C(5)C(4a)C(4)H(4 ax ) is 65°, while the angle C(5)C(4a)C(4)H(4 eq ) is 52°.…”

Organocatalytic C–H activation reactions

“…tert- Amino effect: The “ tert -amino effect” refers to the ring-closure reactions that proceed by redox processes for C–C and C–X bond formation within conjugated systems [7–9]. One well-known example of the “ tert -amino effect” is the cyclization of N , N -dialkyl-substituted anilines with imines to generate cyclic aminals.…”

The homologous tert-amino effect: a route to fused 2-benzazepine derivatives

“…16e19 These efforts are summarized in the recent reviews. 20,21 Moreover, recently tertamino effect type reactions were reported for biphenyl, 22 1,2-bis (aryl)arene, 23 and peri-naphthalene 24 systems. In the course of our research 12,16 on the tert-amino effect we have taken an interest in the compounds of type 8,9 (Scheme 2), the homologs of derivatives 1 with benzene and tertiary amine moieties separated by methylene group.…”