Stereospecific Synthesis of Optically Active Phenylpropylene Oxides

Abstract

The stereospecific lithiation of diastereomeric phenylpropylene oxides has been studied as well as the trapping reaction with electrophiles. The reduction of the cis-alpha-benzoylpropylene oxide to give prevalently the anti-epoxy alcohol has been investigated as well.

Complexation Phenomena and Dynamics at Work in the Lithiation Reactions of Small‐Ring Heterocycles: Regio‐ and Stereoselectivity

“…[13] Treatment of (1S,2S)-4 with sBuLi and TMEDA at -98°C furnished the expected oxiranyllithium (1S,2S)-5 which was stereospecifically trapped with electrophiles with retention of configuration, thus allowing the synthesis of trisubstituted epoxides (1S,2S)-6. [13] Treatment of (1S,2S)-4 with sBuLi and TMEDA at -98°C furnished the expected oxiranyllithium (1S,2S)-5 which was stereospecifically trapped with electrophiles with retention of configuration, thus allowing the synthesis of trisubstituted epoxides (1S,2S)-6.…”

Formation of Olefins by Eliminative Dimerization and Eliminative Cross‐Coupling of Carbenoids: A Stereochemical Exercise

“…[52] 3.2. Eliminative Dimerization of a-Lithiooxiranes a-Metalated oxiranes [53] can be generated by ar ange of methods,i ncluding direct lithiation [20,43,[54][55][56] and various metal-metaloid exchange processes,f or example,t in-lithium [35] and sulfoxide-metal [18b,19] exchange.L ithiated epoxides are chemically and configurationally stable for short time periods at low temperature (typically < À90 8 8C) and the requisite precursors are easily obtained in enantiopure form. Thus,o pportunities exist for exploring the eliminative dimerization of these types of carbenoids in racemic or scalemic modes.T he inaugural encounter with such ap rocess was unintended, when an attempted halogen-lithium exchange of o-chlorostyrene oxide (41)instead resulted in lithiation at the benzylic position [Eq.…”

“…[55] An ensuing eliminative dimerization of the transient racemic lithiooxirane 42 gave the tetrasubstituted olefin product 43 as an unspecified mixture of stereoisomers.Inother studies it was found that the presence of donor solvents or TMEDAslows down the dimerization of lithiated styrene oxides similar to 42 to the point that they can be trapped in high yields by electrophiles. [20,56] Tin-lithium exchange provides am ore general entry to lithiooxiranes than does direct lithiation because precursor stannyl epoxides of any desired regiochemistry and stereochemical configuration can be prepared. Pfaltz and co-Scheme 6.…”

Microreactor Technology in Lithium Chemistry

“…[75][76][77]. Moreover, by repeating the sequence of deprotonation and the reaction with an electrophile using an integrated flow microreactor, diastereoselective synthesis of tetrasubstituted epoxides has been achieved.…”