Phosphates d'énols-X. Détermination des isomères géométriques diversement substitués par résonance magnétique nucléaire

Abstract

R e~u le 28 marsLa configuration des phosphates tnoliques E et Z , substituts sur le premier atome de carbone de la double liaison, a t t t dtterminte dans 27 cas, en utilisant les constantes de couplage 4Jp~c=c-H et les constantes d'tcran selon la mtthode de Tobey-Pascual. Les facteurs qui influencent les constantes de couplage 4 J~~~=~-~ et 5 J~~~=~-~~, sont discutts.The E and Z configuration of en01 phosphates substituted on the first carbon of the double bond are determined, in 27 cases, using4JpoC=C-H coupling constants and the Tobey-Pascual substituent shielding constants method. The factors influencing 4Jp0C=C-H and 5Jpoc=c-c,i, coupling constants are discussed.

Phosphorylation of alkyl-2-chloro-2,3-epoxyalkanoates with trialkyl phosphites: A novel approach to alkyl 2-diethoxyphosphoryloxy-2-alkenoates

“…1 H NMR data of (E) and (Z)-7a corresponded well to those previously reported [9]. Configurational assignments for (E) and (Z)-7b-h were made mainly on the basis of 4 J POCCH , which revealed characteristic larger values for (E) than for (Z) isomers [10]. The yield of particular reactions depended strongly on the spatial structure of the trialkyl phosphite used and decreased dramatically with increasing size of the alkoxy groups connected to the phosphorus atom; in contrast to satisfactorily occurring phosphorylations of 6a and 6c with trimethyl phosphite, analogous phosphorylations with triisopropyl phosphite were ineffective and were accompanied by competitive formation of side products, which were difficult to identify.…”

Mechanistic and synthetic aspects of the reaction of γ-halogeno-α,β-unsaturated ketones and esters with simple trialkyl phosphites

“…Analysis of the 1 H NMR spectrum of this mixture revealed the expected difference in chemical shifts of the H-2 protons in (E )-and (Z )-14c (6.41 ppm and 6.03 ppm, respectively), resulting from the deshielding effect of the cis oriented phosphate group. 7 The H-2 proton in 1,3-dienyl phosphate 14c had a chemical shift at 6.03 ppm proving the Z configuration of this compound. On the basis of the similarity of the spectral data, Z stereochemistry was also assigned to the C-1 double bond of the 1,3-dienyl phosphate 14a.…”

The design and synthesis of β‐trifluoromethylenol phosphates as potential insecticides

“…Trifluoromethylation maintains configuration [8], trifluoromethylenol phosphates made from Z-ß-bromoenol phosphates are also Z-isomers. The E and Z configurations of all enol phosphates were determined using the Tobey-Pascual substituent shielding constant method [9] and NOE observation in NMR.…”