65697-35-0Relevant academic research and scientific papers
Steric and electronic effects in the diastereoselective catalytic epoxidation of cyclic allylic alcohols with methyltrioxorhenium (MTO)
Adam, Waldemar,Mitchell, Catherine M.,Saha-Moeller, Chantu R.
, p. 785 - 790 (2007/10/03)
The steric effects of allylic substituents in the epoxidations with methyltrioxorhenium/urea/hydrogen peroxide adduct (MTO/UHP) have been assessed for a series of 3-alkyl-substituted cyclohexenes. The trans selectivity increases with the size of the substituent and the diastereoselectivities follow an excellent linear correlation with the steric substituent constants of Taft (E(s)) or Charton (v). Good cis selectivity is observed in the epoxidation of the cyclic allylic alcohols 2-cyclopentenol and 2-cyclohexenol due to a hydroxy-directing effect through hydrogen bonding; however, for 2-cycloheptenol and 2-cyclooctenol hydrogen bonding is ineffective and steric interactions cause a higher trans selectivity. The conformationally fixed cis- and trans-5-tert-butyl-2-cyclohexenols serve as suitable substrates for gauging the dihedral angle of the transition states for the oxygen transfer in these epoxidations. Thus, the MTO/UHP oxidant favours a quasi-equatorial arrangement of the hydroxy group for effective hydrogen bonding (hydroxy-group directivity), in analogy to m- chloroperbenzoic acid (m-CPBA) and dimethyldioxirane (DMD), and a dihedral angle of ca. 130°is suggested.
Direct Epoxy Alcohol Synthesis from Cyclic Olefins Using O2 and VO(acac)2-AIBN Catalyst System
Kaneda, Kiyotomi,Jitsukawa, Koichiro,Itoh, Takashi,Teranishi, Shiichiro
, p. 3004 - 3009 (2007/10/02)
The vanadium-catalyzed oxidation of cyclic olefins with molecular oxygen is examined.The VO(acac)2-AIBN system is an efficient catalyst for epoxy alcohol synthesis.Chloro hydrocarbons such as 1,2-dichloroethane and 1,1,2-trichloroethane are suitable solvents for the epoxidation reaction.Cyclohexene (1), methylcyclohexene (2), and cyclododecene (5) give the corresponding epoxy alcohols in good yields; in the case of 2 with VO(acac)2-AIBN system, the selectivity to epoxy alcohol reaches over 70percent. 1,4-Cyclooctadiene (7) is oxidized to give 9-oxabicyclonon-3-en-exo-2-ol (6a) via the rearrangement of cis-2,3-epoxycyclooct-4-en-1-ol.Exceptional is cyclooctene (4), which gives exclusively cyclooctene oxide (4b).
