Enantioselective Addition of Pyrazoles to Dienes

Abstract

We report the first enantioselective addition of pyrazoles to 1,3-dienes. Secondary and tertiary allylic pyrazoles can be generated with excellent regioselectivity. Mechanistic studies support a pathway distinct from previous hydroaminations: a Pd(0)-catalyzed ligand-to?ligand hydrogen transfer (LLHT). This hydroamination tolerates a range of functional groups and provides a breakthrough in hydrofunctionalization of dienes. <br>

Stereoselective Pd-Catalyzed Remote Hydroamination of Skipped Dienes with Azoles

“…These results are quite different from the reaction between conjugated diene and pyrazole reported by Dong who observed the deuteration exclusively at the terminal carbon center. 10 Combined with our prior mechanistic study work on migratory allylic alkylation, 16 we thus provided a plausible mechanism as depicted in Scheme 5 . First, the low-valent Pd(0) was oxidized by protonated base to generate palladium hydride.…”

“…Although the mechanism for Pd-catalyzed hydroamination with conjugated diene and pyrazole was studied in detail, and a ligand-to-ligand hydrogen transfer (LLHT) process was proposed, 10 we guessed the present system might be different due to the involvement of metal walking. First, a control experiment was conducted (Scheme 4a ).…”

“…8 Yang and Dong also developed an efficient protocol for Pd-catalyzed asymmetric hydroamination with conjugated dienes. 10 However, a totally different strategy through remote hydrofunctionalization with skipped dienes and azoles has never been reported (Scheme 1b ).…”

Experimental and theoretical studies of the rhodium(i)-catalysed C–H oxidative alkenylation/cyclization ofN-(2-(methylthio)phenyl)benzamides with maleimides

“…Thus, the reaction is proposed to proceed through an anomalous type of LLHT process involving Rh catalysis which is rare compared to other catalysis such as Ni [24][25][26][27] , Mn, 28 Mo, 29 or Pd. 30 Several alternative paths were also considered for the formation of the final product (isoindolone spirosuccinimides) from N-(2-methylthio)phenyl)benzamides. Thus, three alternative paths were considered and examined after the recoordination of COD to the Rh complex (INT-8).…”