Cascade Chan‐Lam C−O Coupling/[3,3]‐Rearrangement of Arylhydroxylamines with Arylboronic Acids Toward NOBIN Analogues

Abstract

Herein, we developed a copper‐mediated Chan‐Lam type O‐arylation of arylhydroxylamines with arylboronic acids to generate transient N,O‐diarylhydroxylamines that could rapidly undergo cascade [3,3]‐sigmatropic rearrangement and rearomatization to afford NOBIN (2‐amino‐2′‐hydroxy‐1,1′‐binaphthyl) analogues under mild conditions. The newly synthesized racemic biaryl products can be further resolved by a chiral DMAP‐catalyzed O‐acylation/kinetic resolution protocol.

Diverse and chemoselective sigmatropic shift rearrangements of multisubstituted N,O-diarylhydroxylamines

“…To investigate the influence of electronic effect on the chemoselectivity in the sigmatropic shift rearrangement, N , O -diarylhydroxylamine 13f with electron-donating substituents on both the aryl groups was prepared via the copper-catalyzed Chan–Lam C–O coupling of N -acetyl- N -(4-methylphenyl)hydroxylamine ( 11f ) and 2,4,6-trimphenylboronic acid ( 17 ). However, similar to the previously reported cascade Chan–Lam C–O coupling/[3,3] sigmatropic shift rearrangement, 9 a [3,3] sigmatropic shift occurred in situ after the formation of N , O -diarylhydroxylamine 13f and the [3,3] sigmatropic shift product 18 tautomerized into the final product ketonic acetamide 19 in 42% yield. The ketonic acetamide 19 did not generate the corresponding 4a,9a-dihydro-9 H -carbazole derivative 20 due to weak nucleophilicity of the acetamide group although carbazole derivatives are usually generated as byproducts in the [3,3] sigmatropic shift of N , N ′-diarylhydrazines 5 a (Scheme 3).…”

“…The results are in good accordance with the rearrangement of N , N -diarylhydrazines, 5 namely, N , N -diarylhydrazines with electron-donating groups on both of aryl groups favour [3,3] or [5,5] sigmatropic shift rearrangements, 5 a while N , N -diarylhydrazines with electron-donating aryl groups on one nitrogen atom and electron-withdrawing aryl groups on the other nitrogen atom predominantly undergo the [1,3] sigmatropic shift of the N atom with the electron-withdrawing aryl groups. 5 b,c N , O -Diarylhydroxylamines 13af–dg with electron-withdrawing O -aryl groups favour the O[1,3] sigmatropic shift rearrangement, while those with ortho -unsubstituted N - and O -aryl groups, 9 even with electron-rich 2,4,6-trisubstituted O -aryl groups, prefer the [3,3] sigmatropic shift rearrangement.…”

Copper-Catalyzed Reactions of Alkenyl Boronic Esters via Chan–Evans–Lam Coupling/Annulation Cascades: Substrate Selective Synthesis of Dihydroquinazolin-4-ones and Polysubstituted Quinolines

“…In this context, a variety of cascade processes that involve the copper-catalyzed in situ generation and cyclization of C–N bonds have been developed to access diverse N-heterocycles . Among these, the Chan–Evans–Lam (CEL) reaction, an oxidative coupling process from an organoboron and a N-nucleophile, has been merged into an array of one-pot sequential or cascade cyclization reactions …”

Synthesis of ortho-Phosphated (Hetero)Arylamines through Cascade Atherton–Todd Reaction/[3,3]-Rearrangement from Arylhydroxylamines and Dialkyl Phosphites

“…Ortho -phosphated anilide 3e can be dephosphorylated in the presence of LDA to form ortho -hydroxylated anilide 4 in 75% yield (Scheme b) in the presence of NBS and copper-mediated Chan–Lam coupling with 4-tolylboronic acid in good yields (Scheme c,d). The structure of compound 6 was further confirmed by single-crystal X-ray diffraction analysis.…”