49662-27-3Relevant academic research and scientific papers
Stereochemical Consequences of Halogen Atom Substitution. 1. Rotational Conformer Effects in Gaseous Diastereomeric 2,3-Dihalobutanes
Sharma, Ram B.,Ferrieri, Richard A.,Meyer, Richard J.,Rack, Edward P.,Wolf, Alfred P.
, p. 2316 - 2320 (1990)
The stereochemical consequences of translationally excited 38Cl-for-X (X = F, Cl) substitution in (2S,3R)-meso- and (2S,3S)-dl-difluorobutane, (2S,3R)-dl- and (2S,3R)-dl-chlorofluorobutane, and (2S,3R)-meso- and (2S,3S)-dl-dichlorobutane were studied in the gas phase.Although retention of configuration was determined to be the dominant substitution pathway, substantial inversion product yields were observed in all cases.A comparison of these yields revealed that the (S,R) configuration within each set always gave a smaller yield of the inverted product than the (S,S) configuration.This observation was consistent with the hypothesis that back-side substitution was a direct mechanism and that steric hindrance to such attack was subject to differences in the rotational conformer populations within each substrate configuration.In contrast, the measured yields of retention products were insensitive to substrate configuration.
Conformation in 2,3-Difluorobutanes
Angelini, G.,Gavuzzo, E.,Segre, A. L.,Speranza, M.
, p. 8762 - 8766 (2007/10/02)
A conformational analysis for meso- and d,l-2,3-difluorobutanes has been carried out, employing 1H and 19F NMR and theoretical calculations.The real configurations of the two isomers were assigned by specific optical rotation measurements of the products coming from an optically active precursor.Gauche conformations were predominant for meso (E) isomer, while the d,l (T) isomer showed all possible staggered rotamers almost equally populated.Finally remarks for NMR peak assignment of homo- and copolymers partially fluorinated by using gauche additive effects are given.
SYNTHESIS OF OPTICALLY PURE COMPOUNDS BY ENANTIOTOPICALLY DIFFERENTIATING MONOACETALIZATION OF PROCHIRAL DIKETONES. PART II. FRAGMENTATION OF β-KETO-ACETALS
Duthaler, Rudolf O.,Maienfisch, Peter
, p. 832 - 844 (2007/10/02)
Treatment of β-keto-acetals, derived from non-enolisable β-diketones, with sulfonic acids in boiling benzene results in a smooth retro-Claisen-type fragmentation.The acetal-C-atom is thereby transformed into a carboxylic ester via a dialkoxycarbenium ion, which is dealkylated by the sulfonate counter-ion.Application of this reaction to the diastereomeric monoacetals 3 and 4, derived from cis-9-methyl-decalin-1,8-dione (1), followed by transesterification with CH3OH, yields optically pure 4-(2'-methyl-3'-oxocyclohexyl)butyrate 9 ((+)-9 from 3, (-)-9 from 4) and the monosulfonate of meso-2,3-butanediol (-)-13 (Scheme 2).Unexpected, this cleavage proceeds as well with monoacetal 26, obtained by acetalization of trans-9-methyl-decalin-1,8-dione (27) with 2,2-dimethyl-1,3-propanediol (Scheme 7).Some attempts, aiming at an isomerization of the cis- and trans-decalin derivatives 3 and 24, or 25 and 26, via the postulated carboxonium intermediate, were not successful.
