61997-67-9Relevant academic research and scientific papers
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lithio-epoxides thereby generated can be quenched with various reagents to yield epoxides where the epoxide H has been replaced by D, Me3Sn, R, RCO and COOH.The utility of this procedure in organic synthesis is emphasized.Finally, the possible explanations for the acidity of such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.
Stereochemical studies on the formation of α,β-epoxysulfones using α-chloro-β-hydroxysulfones of known configuration
Grossert, J. Stuart,Sotheeswaran, Subramanian,Dharmarante, H. Ranjith W.,Cameron, T. Stanley
, p. 2870 - 2879 (2007/10/02)
Substitution reactions adjacent to sulfonyl groups are known to proceed with difficulty, and there is evidence to suggest that these may not necessarily proceed by an SN2 pathway.The mechanism of these reactions could be studied in principle by using the conversion of α-chloro-β-hydroxysulfones of known configuration into α,β-epoxysulfones of known configuration.This paper describes results in which this has been attempted.However, the stereochemical aspects of the epoxide formation could not be assigned unequivocally because of the intervention of a very facile "retro-aldol" process when the chlorohydrins are subjected to treatment with bases, although the experimental results do suggest that the reaction does proceed in a regular SN2-like manner, with inversion at carbon.The X-ray crystal structures of two highly substituted α,β-epoxysulfones are presented, thus putting the structures, including stereochemistry, of a range of these compounds of firm ground.
