(Z)-3-Methyl-3-penten-2-ol as stereochemical probe for 1,2 versus 1,3 allylic strain in the photooxygenation and epoxidation of chiral allylic alcohols

A Comparison of Intrazeolite and Solution Singlet Oxygen Ene Reactions of Allylic Alcohols

“…2). Allylic alcohol, 4-methyl-3-buten-2-01, 6, was a key substrate in the elegant work of Adam and coworkers (9,(15)(16)(17)(18)(19)(20) that was used to establish the importance of hydrogen bonding as a directing element in singlet oxygen ene reactions. Three rotomers of the S enantiomer of 6 are shown in Fig.…”

Vanadium‐Catalyzed Asymmetric Epoxidation of Allylic Alcohols Mediated by (+)‐Norcamphor‐Derived Hydroperoxide

“…[29] Alcohol 3i was converted exclusively to the erythro epoxy alcohol although with comparable asymmetric induction and efficiency of kinetic resolution [30] (entry 9). The level of diastereoselectivity was better than that observed when using other common systems such as Ti(OiPr) 4 /L-DET/TBHP, Ti(OiPr) 4 /TBHP and VO(acac) 2 /TBHP, [5,31] which preferentially furnished the erythro [32][33][34][35] isomer of 4i. Surprisingly, experiments performed in the absence of ligand afforded, in a shorter reaction time, exclusively the erythro epoxy alcohol (entry 10) with only a marginal effect on the kinetic resolution.…”

Allylic CH Oxidation versus Epoxidation of 2-Cyclohexenols, Catalyzed by Chromium- and Manganese-Substituted Polyoxometalates and Salen Complexes

“…In contrast, for the substrate 7b with only 1,2-allylic strain (entry 2), a negligible diastereoselectivity (48:52) was found. When 1,2-and 1,3-allylic strain are both competing in the same molecule, as in the stereochemical probe 7c, [16] the epoxidation is still highly (81:19) threo-selective. A comparison of these threo:-erythro diastereoselectivities with those of established oxidants (Table 4) suggests that the dihedral angle α in the transition structure with the manganese(salen) oxidant lies between that for Ti(OiPr) 4 /TBHP (70Ϫ90°) [17] and m-CPBA (120°).…”