Catalytic Synthesis of Dibenzazepines and Dibenzazocines by 7‐Exo‐ and 8‐Endo‐Dig‐Selective Cycloisomerization

Abstract

The 7‐exo‐ and 8‐endo‐dig‐selective gold‐catalyzed cycloisomerizations of 2‐propargylamino biphenyl derivatives were developed. The reaction of terminal alkynes gave dibenzo[b,d]azepines by 7‐exo‐dig cycloisomerization. In contrast, when internal alkynes were subjected to the reaction, 8‐endo‐dig cycloisomerization proceeded to provide dibenzo[b,d]azocines. The nucleophilicity at the reaction site and the electron‐withdrawing effect of a tosyl group were important for the present selective transformation. This protocol could be used for ynamide substrates and a silver‐catalyzed reaction gave 7‐exo‐dig products selectively.

Homogeneous Gold Catalysis for Regioselective Carbocyclization of Alkynyl Precursors

“…By indulging 2‐propargylamino biphenyls 3.18 under Au(I)‐NHC catalysis, Tanaka et al . showed the regiochemical course can be controlled by the choice of terminal or internal alkyne tether (Scheme 18, top) [135] . While 7‐ exo ‐ dig selectivity is observed with terminal alkynes leading to 3.19 , the regio‐competing 8‐ endo ‐ dig mode of cyclization is witnessed in internal alkynes to form 3.20 .…”

“…[134] By indulging 2-propargylamino biphenyls 3.18 under Au(I)-NHC catalysis, Tanaka et al showed the regiochemical course can be controlled by the choice of terminal or internal alkyne tether (Scheme 18, top). [135] While 7-exo-dig selectivity is observed with terminal alkynes leading to 3.19, the regiocompeting 8-endo-dig mode of cyclization is witnessed in internal alkynes to form 3.20. This shift in regioselectivity with respect to substituent variation at the alkyne terminus is explained from the grounds of steric repulsion and cation stability of prototype substrate 3.18 a (Scheme 18, bottom).…”

Computational insight into gold(i)-catalyzed intramolecular regioselectivity of tryptamine-ynamide cycloisomerizations

“…[1][2][3][4][5][6][7][8] The reaction pathways of these cycloisomerizations are determined by a variety of parameters, such as solvents, [9][10][11][12] catalysts, [13][14][15] ligands, [16][17][18][19][20] and substitutions. [21][22][23][24][25][26] These pathway-switchable reactions enable chemists to synthesize molecules with different scaffolds from the same or similar reactants only by tuning these parameters of the reactions. They afford a useful synthetic toolbox for generating small molecules through divergent pathways, which can improve the efficiency of organic reactions.…”

Gold(I)-Catalyzed Substitution-Controlled Syntheses of Spiro[indoline-3,3′-pyrrolidine] and Spiro[indoline-3,3′-piperidine] Derivatives

“…Gold-catalyzed cycloisomerizations of 1, n -enynes are atom-economical and straightforward transformations to generate functionalized carbo- and heterocycles via readily available substrates . The reaction pathways of these cycloisomerizations may be altered by a variety of parameters, such as solvents, catalysts, ligands, substitutions, and so on. For example, Fernández-Rodríguez and co-workers reported that a gold-catalyzed cycloisomerization of embedded trienynes could be used to synthesize phenanthrenes or dihydrophenanthrenes by changing the reaction solvents .…”