Two Novel Thermal Biradical Cyclizations of Enyne-Ketenimines: Theory, Experiment, and Synthetic Potential

Abstract

Both benzocarbazoles and quinolines can be synthesized from enyne ketenimines 1 generated in situ via biradical intermediates (see reaction below). Which of the heterocyclic ring systems is formed depends on the choice of the substituent R at the alkyne terminus.

One-pot synthesis of highly functionalized stable ketenimines of 2,2,2-trifluoro-N-aryl-acetamides

“…1 H, 13 C and 19 F NMR spectra were recorded on Bruker DRX-500 Avance spectrometer at 500.13, 125.77 and 470.56 MHz, respectively. 1 H, 13 C, and 19 F NMR spectra were obtained on solution in CDCl 3 using TMS or CFCl 3 as internal standard. 2,2,2-Trifluoro-N-aryl-acetamides were prepared by treatment of anilines and trifluoroacetic acid in microwave [34].…”

“…Ketenimines are important reactive intermediates that occur as transient compounds in many thermal and photochemical reactions [9][10][11][12]. There has been intense interest in their addition reactions, such as cycloaddition [13][14][15], nucleophilic [11,16,17], and electrophilic [18,19] addition. The trapping of the 1:1 intermediate formed between dialkyl acetylenedicarboxylates and isocyanides with OH, NH, and CH acids has been widely studied [20][21][22][23][24].…”

“…Found: C, 56.24; H, 5.32; N, 5.83%.. MS (m/z, %): 470 (M + , 4). 1 H NMR (500.1 MHz, CDCl 3 ): d = 1.21-1.78 (10 H, 5 CH 2 of cyclohexyl), 3.62 (1 H, m, CH of cyclohexyl), 3.37 (3 H, s, OCH 3 ), 3.70 (3 H, s, OCH 3 ), 3.79 (3 H, s, OCH 3 ), 5.63 (1 H, s, CH), 7.25-7.35 (4 H, aromatic) ppm 13. C NMR (125.7 MH Z , CDCl 3 ): d = 23.1, 24.2, 25.2, 33.3 and 33.4 (5 CH 2 of cyclohexyl), 52.2 (OCH 3 ), 53.0 (OCH 3 ), 53.4 (OCH 3 ), 57.2 (CH of cyclohexyl), 60.9 (N C C), 62.3 (CH), 118.2 (q, 1 J FC = 286 H Z , CF 3 ) 128.9, 130.3, 133.5 and 137.8 (C aromatic), 157.2 (q, 2 J FC = 36 H Z , COCF 3 ), 160.59 (N C C), 169.81 (CO 2 Me), 171.28 (CO 2 Me) ppm.…”

Synthesis of Ketenimines Derivatives from Reaction between Alkyl Isocyanides and Dialkyl Acetylenedicarboxylates in the Presence of Carboxylic Acid Arylidene-Hydrazides

“…There has been intense interest in their addition reactions, such as cycloaddition [3][4][5] Multicomponent reactions (MCRs), by virtue of their convergence, productivity, facile execution and generally high yields of products, have attracted much attention in the area of combinatorial chemistry [6][7][8] , of pivotal importance are the isocyanidebased MCRs 9 . The trapping of the 1:1 intermediate formed between dialkyl acetylenedicarboxylates and isocyanides with OH, NH and CH acids has been widely studied [10][11][12][13][14][15][16] .…”

Three-Component Reaction of Alkyl Isocyanides, Dialkyl Acetylenedicarboxylates and Furan-2-Carboxylic Acid Arylidene-Hydrazides

“…1,2 There has been intense interest in their addition reactions, such as cycloaddition [3][4][5] and nucleophilic, 6,7 electrophilic, 8,9 and radical addition. [10][11][12][13] In addition, novel synthetic approaches to carbocyclic and N-heterocyclic four-, five-, and six-membered rings using ketenimine transitionmetal complexes have been developed.…”