Strained rings to assess the "endo preference" of 2-alkyl branched 2-alkenylpotassium species
Upon deprotonation using trimethylsilylmethylpotassium or butyllithium in the presence of potassium tert-butoxide, two allylic organopotassium species are generated from the (E)-isomeric caryophyllene and the (Z)-isomeric isocaryophyllene. Torsional equilibration occurs slowly at -50 DegC (in THF) and rapidly at 0 DegC (in hexane) to afford endo/exo-mixts. of about 95:5 (as evidenced by the isomeric compn. of the trapping products). The relative thermodn. stabilities of the two stereoisomeric organometallic intermediates can be derived by mere superposition of ring-strain differences and the "endo preference" of open-chain (alkylalkenyl)potassium compds. [on SciFinder (R)]
Keywords: Addition reaction; Substitution reaction (boration; ring strain in metalation ; borylation and oxidn. of caryophyllene and isocaryophyllene); Free energy; Stability; Stereochemistry; Strain energy; Substituent effects (ring strain in metalation ; borylati ; alkenylpotassium prepn potential energy strain; substituent effect strain oxidn caryophyllene isocaryophyllene; potential energy strain oxidn caryophyllene isocaryophyllene; caryophyllene alkenylpotassium prepn; isocaryophyllene alkenylpotassium prepn
Physical Organic Chemistry
Institut de Chimie organique de l'Universite,Lausanne-Dorigny,Switz.
written in English.
78683-81-5P; 79768-25-5P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. of); 87-44-5 (Caryophyllene); 118-65-0 (Isocaryophyllene) Role: RCT (Reactant), RACT (Reactant or reagent) (ring strain in metalation, borylation and oxidn. of caryophyllene and isocaryophyllene)
Record created on 2006-03-03, modified on 2016-08-08