Preparation of α,β-Unsaturated Aldehyde Dimethyl Acetals and their Free Aldehydes

Abstract

centration was estimated on the basis of equation 10, to give an approximate value of 2 X 10-3 l.2 mole-2 sec.-1 for k¡, at 30°.Values for the rate constants k-¡ and ki were obtained at 10, 20, 30 and 40°. These results are summarized in Table IV along with the energies of Table IV Summary of the Rate Constants at Various Temperatures AND OF THE ENTHALPIES AND ENTROPIES OF ACTIVA-Temp., °C. Equation 2°Equation 36 kc 10 (2.6 dr 0.2)10-2 (0.86 ± 0.01)10-= kc 20 o -H CO (2.2 ± ,l)10-= k°30(9.9 ± .3)10-2 (6.7 ± ,2)10-= kc 40 (13.8 ± 1.2)10-2 (14.3 ± .4)10-= ±, kcal.10.6 16.15±, e.u. 30-28.2 -24.6 " The units of fe2 are l.2 mole-2 sec.1. 6 The units of kz are 1. mole-1 sec. l. = The measure of the precision is the standard deviation of the average values used.

Novel Preparation of α,β-Unsaturated Aldehydes. Benzeneselenolate Promotes Elimination of HBr from α-Bromoacetals

“…Although the acetalization/bromination/nucleophilic selenenylation/oxidation/hydrolysis sequence for dehydrogenation of aldehydes proposed in the lower part of Scheme involves one or two steps more than procedures commonly used, it is a general and versatile method that could find synthetic use for the preparation of a variety of α,β-unsaturated aldehydes. The competing elimination reaction observed in the substitution of branched or tertiary bromoacetals with benzeneselenolate (resulting in the formation of α,β-unsaturated acetals) is by no means disturbing since the product can be readily hydrolyzed to the desired enal . Olefin formation is intriguing from a mechanistic point of view, though.…”

Plasmalogens. I. The Synthesis of 1-Alkenyl Ethers of Glycerol1,2

“…18 The boiling points and refractive indices of these compounds correspond satisfactorily to those reported in the literature. 19•20 The method of Bedoukian19 was employed for preparing 2-bromo-lrl-dimethoxyhendecane.…”