104832-82-8Relevant academic research and scientific papers
Synthesis and stuctures of moderately stable metallaxoetanes: (η5-C5Me5)2(CH 3)TaOCHRCH2= (R=H, C6H5) investigations of their decompositon to olefin and (η5-C5Me5)2 Ta(=O)CH3
Whinnery Jr., LeRoy L.,Henling, Lawrence M.,Bereaw, John E.
, p. 7575 - 7582 (2007/10/02)
Metallaoxetanes Cp*2(CH3)TaOCHRCH2 (Cp* = ((η5-C5Me5); R = H, p-C6H4X; X = H, Cl, CF3, CN, NO2) have been prepared by reaction of Cp*2Ta(=CH2)CH3 with the appropriate aldehyde RCHO, The kinetic products of the 2 + 2 reaction between the benzaldehydes with Cp*2Ta(==CH2)CH3 are O-syn-Cp*2)(CH3)TaCH2)CH(p-C 6)H4X)O, which rearrange in benzene solution at 25°C to the more O-anti-Cp*2(CH3)TaCH2CH(p-C 6H4X)CH2. An X-ray crystal structure determination for O-anti-Cp*2(CH3)TaOCH(C6H 5)CH2 has been carried out (space group P21/c (No. 14) with cell parameters a = 15.677 (10) A?, b = (4) A?, c = 18.315 (18) A?, β= 110.81 (7)°, V= 2550.3 (32) A?3, and Z = 4), a puckered four-membered ring. The distortion from planarity likely arises from close contacts between a pentamethylcyclo-pentadienyl ligand and the phenyl ring. Decomposition of O-anti-Cp*22(CH3)TaOCHRCH2 smoothly at 80°C to afford Cp*2Ta(=O)CH3 and RCH=CH2. The rates for styrene formation depend only slightly on the para substituent and do not correlate with σ orσ=. In a related transformation, Cp*2Ta(=CH2)H reacts with epoxides in THF even at -50°C to yield Cp*2Ta(=O)CH3 and olefin. Significantly, neither Cp*2Ta(=O)CH3 nor O-syn-Cp*2(CH3)-TaCH2CH2O nor O-anti-Cp"2is observed as an intermediate for the deoxygenation of ethylene oxide, and deoxygenation of trans-styrene-d1(CH3) TaOCH2CH2 is observed as an intermediate for the deoxygenation of trans-styrene-d1 oxide, trans-ethylene-d2 oxide with >95% retention of stereochemistry. These result strongly implicate a concerted process and indicate that epoxide deoxygenation and (more importantly) olefin epoxidation with transition-metal derivatives need not involve metallaoxetane intermediates.
Synthesis of (2R,3R)- and (2S,3S)-Oxirane and Application of It to the Synthesis of Chirally Labeled Homoserine
Schwab, John M.,Tapan, Ray,Ho, Chorng-Kei
, p. 1057 - 1063 (2007/10/02)
(2R,3R)- and (2S,3S)-oxirane have been synthesized from 2-propynol, the key step being the asymmetric epoxidation of (E)-3-(triphenylsilyl)-2-propenol.To determine the enantiomeric purities of the oxiranes, they were reacted with phenyllithium,
Organosilicon compounds with functional groups proximate to silicon. XVII. Synthetic and mechanistic aspects of the lithiation of α,β-epoxyalkylsilanes and related α-heterosubstituted epoxides
Eisch, John J.,Galle, James E.
, p. 293 - 314 (2007/10/02)
A series of α-heterosubstituted epoxides, , has been found to undergo lithiation in the temperature range of -75 to -115 deg C at the C-H bond of the epoxide.The substituent Z could be Me3Si, Ph3Si, n-Bu3Sn, Ph3Sn, PhSO2, (OEt)2PO and Ph; the groups R and R' were H, Ph and n-C6H13; and the lithiating reagents were n-butyllithium, t-butyllithium and lithium diisopropylamide in donor media of THF or TMEDA.The lithiation occurs with retention of configuration and the resulting lithio-epoxide is unstable above 0 deg C, decomposing in a carbenoid manner.The lithiation is facile except for compounds where Z and R (an alkyl or aryl) are cis-oriented; where Z = R3Sn, lithiation occurs by tin-lithium, rather than hydrogen-lithium, exchange.The lithio-epoxides thereby generated can be quenched with various reagents to yield epoxides where the epoxide H has been replaced by D, Me3Sn, R, RCO and COOH.The utility of this procedure in organic synthesis is emphasized.Finally, the possible explanations for the acidity of such α-heterosubstituted epoxides and for the relative stability of the derived lithio-epoxides are considered and assessed.
Chirally-labelled Oxirane
Schwab, John M.,Ho, Chorng-Kei
, p. 872 - 873 (2007/10/02)
(R,R)- and (S,S)-oxiranes have been synthesized from prop-2-yn-1-ol, the key step being asymmetric epoxidation of (E)-3-(triphenylsilyl)prop-2-en-1-ol.
