Rh₂(II)-Catalyzed Selective Aminomethylene Migration from Styryl Azides

Abstract

Rh(2)(II)-carboxylate complexes were discovered to promote the selective migration of aminomethylenes in β,β-disubstituted styryl azides to form 2,3-disubstituted indoles. Mechanistic data are also presented that suggest that the migration occurs stepwise before diffusion of the iminium ion.

Development of a Suzuki Cross-Coupling Reaction between 2-Azidoarylboronic Pinacolate Esters and Vinyl Triflates To Enable the Synthesis of [2,3]-Fused Indole Heterocycles

“…Purification by MPLC (2/100 to 10/90 EtOAc/hexanes) afforded the product as a light yellow solid (0.900 g, 76%): spectral data matched those reported by Driver and co-workers; 24 1 H NMR (500 MHz, CDCl 3 ) δ 7.28 (dd, J = 9.0 Hz, 3.0 Hz, 1H), 6.92 (dt, J = 8.5 Hz, 3.0 Hz, 1H), 6.53 (dd, J = 9.0 Hz, 4.5 Hz, 1H), 4.59 (s, 2H), 1.34 (s, 12H); 13 C{ 1 H} NMR (125 MHz, CDCl 3 ) δ 155.2 (d, J CF = 233.2 Hz, C), 149.8 (C), 121.6 (d, J CF = 20.1 Hz, CH), 119.7 (d, J CF = 23.7 Hz, CH), 116.0 (CH), 83.9 (C), 24.9 (CH 3 ); 19 F NMR (282 MHz, CDCl 3 ) δ −129.5; IR (thin film) 3470, 3371, 2975, 2931, 1624, 1492, 1434, 1380, 1347, 1198, 1190, 1135, 1081, 963, 912 cm –1 .…”

Assembly of functionalized carbocycles or N-heterocycles through a domino electrocyclization–[1,2] migration reaction sequence

“…In every substrate examined, a [1,2] aryl shift occurred exclusively to afford the product irrespective of the electronic nature of the migrating aryl group or the stereochemistry of the starting styryl azide. 103 The authors proposed a γ-heteroatom might control the selectivity of the [1,2] shift reaction by using its lone pair of electrons to trigger C-C bond heterolysis and stabilize the build up of positive charge in the migration. To account for the selectivity of 2-alkyl-3-arylindole formation, the authors proposed the catalytic cycle outlined in Scheme 42.…”

Recent Achievements in the Rhodium‐Catalyzed Concise Construction of Medium N‐Heterocycles, Azepines and Azocines

“…By using N-aryl rhodium nitrenes as the key intermediates from ortho azide styrenes, in 2013, Driver reported an aminomethylene migration involved synthesis of indolazepines (Scheme 27). [24] Notably, compared to well explored oxonium and ammonium ylide induced 1,2-shift, this transformation represents a novel nitrene-facilitated selective 1,2-shift. Mechanistically, when using enantiomerically enriched styryl azides under standard conditions, racemic indole products were obtained, which indicates that the key 1,2-shift might take place in a stepwise manner.…”