Abstract

Elham Aghdaei, Sayyed Mostafa Habibi-Khorassani^*and Mehdi Shahraki

DOI : http://dx.doi.org/10.13005/ojc/310475

A general and practical route has been described for the synthesis of dimethyl-2-[4-bromophenyl phenylcarbamate-N-yl]-3-(triphenylphosphoranylidene) butandioate in excellent yield. The ¹H, ¹³C, and ³¹P NMR data of synthesized phosphorous ylide 5 indicated two rotational isomers as major Z-5 and minor E-5 forms. Dynamic ¹H NMR effect has been investigated around the C=C bonds in the two Z- and E-rotational isomers at variable temperatures. Herein, activation parameters including ΔH^≠, ΔG^≠, ΔS^≠ were also calculated using ab initio and DFT methods at HF/6-31G(d,p) and B3LYP/6-31G(d,p) levels of theory. The experimental and theoretical data indicated that the rotational barrier around the C=C double bond was considerably high and observation of the two rotational isomers was impossible at the high temperatures. The B3LYP level of theory using the 6-31G (d,p) basis set provided more reasonable results in agreement with the experimental data.

Dynamic 1H NMR; Ylide; DFT; Rotational barrier; Ab initio

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