Phenylthio 2-vinylcyclopropyl cuprate

Analysis of Reagent Purity an assay to determine relative thermal stabilities can be used to estimate reagent quality and concentration a sample of known volume and temperature Is quenched with excess PhCOCl the 3deld of 2 vinylcyclopropyl phenyl ketone is measured by GC or UPLC, the response of which is calibrated using authentic product and an appropriate internal standard. 

Preparative Method 2 vinylcyclopropyUlthlum Is prepared by cooling a 0.25 M ether or THE solution of l-bromo-2-vinylcyclopropane under Ar to — 78°C. Dropwise addition of 1.1-1.4 equiv of a solution of ferf-butyllithium is followed by stirring for 2 h. One equiv of phenylthiocopper(I) is added, and the resultant slurry is diluted with 5 mL THF per mmol of cyclopropane. The reaction is warmed to —20 °C a clear, light brown solution of cuprate forms after stirring for 20 min. It is cooled to —78 °C and is used directly. 

Handling, Storage, and Precautions best results are obtained with PhSCu prepared from high purity Cu salts, dry, O2-free solvents, and alkyllithium solutions free of contaminating alkoxides or hydroxides. f-BuLi is pyrophoric care must be exercised In Its handling. Use in a fume hood. 

A list of General Abbreviations appears on the front Endpapers 

Either the cis- or frans-isomer or a mixture of Isomeric 1-bromo-2-vinylcyclopropanes can be used In the reaction, although rearrangement is more facile with the cis-Isomer. The method has been used in a convergent total synthesis of the sesquiterpene /3-himachalene to assemble the 7,6-fused ring core of the natural product. 

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Interesting and useful variations in R involve more complex alkyllithium reagents. For example, the treatment of (3-iodoenone (10) with lithium phenylthio(2-vinylcyclopropyl)cuprate gave the conjugate addition product (11) as an intermediate en route to the bicyclic dienone (12 82% equation 9).35 The ability of a cuprate to deliver a functionalized group to the enone was a definite advantage in this synthetic scheme. 

As an alternative to the addition of vinylcyclopropyllithium derivatives to /5-alkoxycy-cloalkenones, Cope substrates for 1,2 3,4 rearrangements can also be prepared by addition of phenylthio(2-vinylcyclopropyl)cuprate to readily available 3-halo-2-cycloalkenones871 875, e.g., 69, 72, 74, and 77 in tetrahydrofuran/diethyl ether/pentane at —78 to — 20 °C 876. 

Lithium phenylthio [ (a-diethoxymethyl)-vinyl] cuprate, 212-213 Lithium phenylthio(2-vinylcyclopropyl)-... 

Related Reagents. Lithium Bis(2-vinylcyclopropyl)cup-rate Lithium Dimethylcuprate Lithium Methyl (phenylthio) cuprate. 

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