Wavelength Control of Diastereodifferentiating Paternó−Büchi Reaction of Chiral Cyanobenzoates with Diphenylethene through Direct versus Charge-Transfer Excitation
摘要:
In the diastereodifferentiating Paterno-Buchi reaction, the excited CT complex was distinctly different in structure and reactivity from the conventional exciplex, and the inherent diastereofacial selectivity and its temperature dependence were opposite to each other in these two excitation modes. Thus, the combined use of wavelength and temperature not only reveals the mechanistic details but also provides a new. convenient, powerful tool. for critically controlling the stereochemical outcomes of asymmetric photoreactions.
Contrasting Behaviour of Exciplex Ensembles in the Diastereodifferentiating Paternò–Büchi Reaction of Chiral Cyanobenzoate with Naphthyl- and Phenylethenes on Direct or Charge-Transfer Excitation
作者:Keisuke Nagasaki、Yoshihisa Inoue、Tadashi Mori
DOI:10.1071/ch15404
日期:——
direct and charge-transferexcitations. By desymmetrization of the donor, four diastereomeric oxetane products were formed on photolysis in excellent combined yields. Increase in donor strength induced a stronger charge-transfer interaction both in ground and excited states. Thus, the difference in diastereoselectivities with two different excitation modes (i.e. direct versus charge-transfer) became less
Solvent and Temperature Effects on Diastereodifferentiating Paternó−Büchi Reaction of Chiral Alkyl Cyanobenzoates with Diphenylethene upon Direct versus Charge-Transfer Excitation
Paternó−Büchi reaction of chiral p-cyanobenzoates (1) with 1,1-diphenylethene (2), we revealed that the excited charge-transfer (CT) complex formed upon selective excitation at the CT band is distinctly different in structure and reactivity from the conventional exciplex generated through the direct excitation of acceptor 1 which subsequently associates with donor 2. Thus, the favored diastereoface upon photocycloaddition
Wavelength Control of Diastereodifferentiating Paternó−Büchi Reaction of Chiral Cyanobenzoates with Diphenylethene through Direct versus Charge-Transfer Excitation
In the diastereodifferentiating Paterno-Buchi reaction, the excited CT complex was distinctly different in structure and reactivity from the conventional exciplex, and the inherent diastereofacial selectivity and its temperature dependence were opposite to each other in these two excitation modes. Thus, the combined use of wavelength and temperature not only reveals the mechanistic details but also provides a new. convenient, powerful tool. for critically controlling the stereochemical outcomes of asymmetric photoreactions.