A facile and convenient sequential homobimetallic catalytic approach towards β-methylstyrenes. A one-pot Stille cross-coupling/isomerization strategy

Abstract

An efficient one-pot synthetic approach towards β-methylstyrenes is reported. The transformation, based on sequential homobimetallic catalysis, involves a Stille cross-coupling reaction between aryl halides and allyltributylstannane, followed by an in situ palladium-catalyzed conjugative isomerization. The reaction was optimized, and the best results were obtained with 10 mol% Pd(PPh3)2Cl2, 8.0 equiv. LiCl, and 0.5 equiv. PPh3 in diglyme at 130 °C for 12 h. It was demonstrated that the reaction tolerates a wide variety of functional groups.

Isomerization of Allylbenzenes

“…It should also be noted here that Kaufman recently developed an interesting general synthesis of 1-propenylbenzenes based on observations from their aspergillitine synthesis above . In this work, Stille coupling reactions (10 mol % Pd­(PPh 3 ) 2 Cl 2 , LiCl, PPh 3 ) between different aryl halides 321 and allyltributylstannane 322 resulted in a set of 2-propenylbenzenes, which were then isomerized in situ by the same catalyst system to afford a range of E -enriched 1-propenylbenzenes 323 (Scheme ).…”

“…It should also be noted here that Kaufman recently developed an interesting general synthesis of 1-propenylbenzenes based on observations from their aspergillitine synthesis above. 445 In this work, Stille coupling reactions (10 mol % Pd(PPh 3 ) 2 Cl 2 , LiCl, PPh 3 ) between different aryl halides 321 and allyltributylstannane 322 resulted in a set of 2propenylbenzenes, which were then isomerized in situ by the same catalyst system to afford a range of E-enriched 1propenylbenzenes 323 (Scheme 77). The researchers noted that these transformations were evidence of "sequential homobimetallic catalysis" in which the catalyst system was performing two sequential transformations while in different oxidation states, Pd(0) for the Stille C−C coupling and Pd(II) for the isomerization process.…”

Deoxygenation of N‐heterocyclic N‐oxides with Selectfluor and disulfane

“…Moreover, almost all of these conventional methods fail in terms of functional group tolerance. Efforts toward using nontraditional activation methods such as photoredox reactions [6a, 13] and electrochemistry [14] also include metal moieties or moderate product yields.…”