Computational study on the Rh‐catalyzed chemodivergent oxidative annulation of benzamides and enynes

Abstract

The mechanisms of Cp*Rh(OAc)2‐catalyzed coupling reaction of N‐methoxybenzamide with alkyl‐terminated enyne have been investigated using density functional theory (DFT) calculations. With the addition of NaOAc, the product transforms from lactam P1 in reaction A to iminolactone P2 in reaction B due to the formed stable OAc− coordinated intermediate. The electronic effect accounts for the observed chemooselectivity in reaction B.

Rh(iii)-Catalysed cascade C–H imidization/cyclization ofN-methoxybenzamides with isoxazolones for the assembly of dihydroquinazolin-4(1H)-one derivatives

“…On the basis of the above results and literature precedents, 3 a ,4 l ,10,11 c we proposed a reaction mechanism for the developed transformation. As shown in Scheme 4, Cp*Rh(OPiv) 2 was initially formed as an active catalyst via anion exchange, which mediated the reversible N–H/C–H cleavage of N -methoxybenzamide 1a to afford intermediate A .…”

“…DFT calculations were carried out using Gaussian 09 by rationally selecting the five-membered rhodacycle INT-1 as the starting point (zero value of energy). 10,11 As shown in Fig. 1, the coordination of isoxazol-5(4 H )-one 2a with the rhodium metal centre of INT-1 afforded INT-2 with a free energy of 0.9 kcal mol −1 , the following N–O bond cleavage via TS-1 (Δ G ‡ = 8.5 kcal mol −1 ) led to the formation of a Rh( v ) species INT-3 .…”