The ¹H, ¹³C and ³¹P NMR spectra of EZ pairs of some phosphorus substituted alkenes

Abstract

The olefins Ph,P(X)CH=CHR [X=lone pair, 0, S, CH31; R=CH3, Ph, P(X)PhJ have been prepared and their 'H, 13C and "P N M R spectra measured. trans 'qP(IV)C] (range 18.3-25.7HzI is greater than cis 3J[P(IV)C] (range 6.9-11 Hz) but this relationship does not hold for P(II1) compounds. In the "P spectra the E isomer absorbs to higher field than the Z isomer for P(II1) and P(IV) compounds. The 'H data are in accord with previous results; average substituent shielding coefficients for Ph,P(X) substituted alkenes are reported.Numerous studies of the 'H, 13C and 31P spectra of various classes of organophosphorus compounds have been published. Both ,J(PH) and ,J(PC) appear to follow a Karplus-type relationship,lZ2 though recent results have shown some unexpected variations when the phosphorus is trivalent.2h However, there are very few data in the literature on the differences expected in the 13C and 31P spectra of EZ alkene pairs. Such information is desirable for structure elucidation and for determining the steric course of reactions. In addition, since replacement of vinylic halogen by phosphorus is chemically simple, and reported to proceed stereo~pecifically,~ the introduction of a spin-active substituent could greatly simplify the analysis of I3C and/or 'H spectra of vinylic halides.We describe here the results of a 'H, 13C and 31P study of eight pairs of geometrical isomers: the phosphines (A; R = CH, or Ph) and their corresponding oxides, sulphides and methiodides. The 31P data for some symmetrical diphosphorus substituted ethenes are also included. Ph,PCH=CHR A EXPERIMENTALThe propenyl and styryl phosphines were prepared by reaction of diphenylphosphinous chloride with the Grignard reagent obtained from the appropriate halide. Commercially available 2-bromostyrene was predominantly the E isomer and a sample of the Z isomer was prepared by the method of Cristol and N o r r i~.~ 1-Bromopropene was largely (c. go0/,) the Z isomer. The stereochemistry of the halides was determined by 'H and 13C NMR and confirmed for the phosphines by isolating the major component of each mixture as its sulphide and oxide and comparing their melting points with literature values. The styrylphosphine 5 Z was isolated as a crystalline solid, m.p. 93-95'. The preparation of the phosphines was * Author to whom correspondence should be addressed. stereoselective though some inversion at vinylic carbon occurred, probably at the Grignard preparation stage. Stereomutation was most pronounced for the 2-styryl compound. Measurements were made only on crystalline 2 isomer obtained from this mixture.The diphosphines were prepared from the corresponding dihalide and lithium diphenylphosphide in tetrahydr~furan.~ The disulphides and dioxides are known compounds and were prepared by conventional methods.3-Methyl-1-0x0-1-phenylphosphol-2-ene (19) was a commercial sample.C and 31P spectra were determined on a Bruker WP-60-FT spectrometer at 15.08 and 24.28 MHz, respectively, using a sweep width of 3750 Hz and 4 K real data points. Carbons without hydr...

Theoretical IPPP analysis of 13C‐31 P through‐space indirect couplings in phosphorus‐substituted alkenes

“…This could account for part of the difference between the couplings calculated here and those in Ref. 1.…”

An Efficient Synthesis of Novel α‐Aminophosphonates Based on a Mannich‐Type Reaction

“…The development of new synthetic strategies towards non-proteinogenic unsaturated α-amino acids remains active since they are important building blocks in the synthesis of biologically active compounds. [19] Our first examples of these α-amino acid surrogates 12 show that our protocol facilitates a general and straightforward access to this promising class of homoallylic derivative.…”

[1,3,4]Thiazaphospholidine. V

“…C 21 H 29 N 3 PS) und C 6 H 5 am Kohlenstoffatom C 2 auf d 31 P wesentlich geringer ist als jener, der durch die E/Z-Konfigurationsa È nderung hervorgerufen wird. Letzteres wurde auch bei den E/Z-Paaren der Alkene R(H)C=C(H)P(C 6 H 5 ) 2 , R = CH 3 , C 6 H 5 und P(C 6 H 5 ) 2 festgestellt; u È berdies sind die Isomeren mit zum Phosphoratom trans-sta È ndigem Kohlenstoffatom von R = CH 3 und C 6 H 5 (E-Konfiguration) ebenfalls bei tieferen Magnetfeldsta È rken zu beobachten, als jene mit cis-sta È ndigem C-Atom (Z-Konfiguration) [8,9].…”