Regio- and Diastereoselective Catalytic Epoxidation of Acyclic Allylic Alcohols with Methyltrioxorhenium: A Mechanistic Comparison with Metal (Peroxy and Peroxo Complexes) and Nonmetal (Peracids and Dioxirane) Oxidants
作者:Waldemar Adam、Catherine M. Mitchell、Chantu R. Saha-Möller
DOI:10.1021/jo9902289
日期:1999.5.1
Geraniol and its 1-methyl derivative (regiochemical probes) and a set of methyl- and tert-butyl-substituted chiral allylicalcohols (stereochemical probes) have been used to elucidate the mechanism of the MTO-catalyzed epoxidation of allylicalcohols. The regiochemical probes are preferentially epoxidized at the unfunctionalized double bond by these MTO-based oxidants, which establishes that MTO/UHP
Cascade Sequence of Photooxygenation–Epoxidation for the Flow Synthesis of Epoxy Alcohols
作者:Ji Eun Kim、Go Eun Son、Hyo Jin Lim、Yea Seul Jang、Chan Ho Song、Chan Pil Park
DOI:10.1021/acs.joc.4c00322
日期:2024.5.17
sequence converting alkenes to epoxy alcohols was developed and evaluated in batch and continuous-flow systems. In the batch system, the undesired interactions between the photooxygenation and epoxidation catalysts resulted in suboptimal yields, whereas the fine control of reaction parameters in the flow system allowed the allyl hydroperoxides produced through photooxygenation of alkenes to be rapidly converted
Diastereoselective Catalytic Epoxidation of Chiral Allylic Alcohols by the TS-1 and Ti-β Zeolites: Evidence for a Hydrogen-Bonded, Peroxy-Type Loaded Complex as Oxidizing Species
The similar diastereoselectivities as for peracids implicate a pentacoordinated metal peroxy species in the epoxidation of chiral allylic alcohols by the titanium-containing zeolites TS-1 and Ti-beta. In the loaded complex, the allylic alcohol substrate is fixed through hydrogen bonding to the metal center, with A(1,3) strain as the dominant conformational feature. By comparison of the diastereoselectivities to those for VO(acac)(2)/t-BuOOH, we exclude a peroxy-type complex with direct coordination of the allylic alcohol to the titanium center by means of metal-alcoholate bonding. Neither does a peroxo-type titanium complex apply, as confirmed by comparing the diastereoselectivities with those observed for dioxiranes. With the help of tert-butyl-substituted allylic alcohols as substrates, which are not epoxidized by the TS-1 but by the Ti-beta catalyst, it was unequivocally confirmed that the oxidation occurs inside of the zeolite and not on the outer surface.