146791-31-3Relevant academic research and scientific papers
Synthesis of Cyclic and Acyclic Enol Ethers (Vinyl Ethers)
Gassman, Paul G.,Burns, Stephen J.,Pfister, Keith B.
, p. 1449 - 1457 (2007/10/02)
A general method has been developed for the conversion of both cyclic and acyclic acetals of cyclic ketones, acyclic ketones, and aldehydes into enol ethers through treatment of the acetal with trimethylsilyl triflate in the presence of N,N-diisopropylethylamine.The range of isolated yields of enol ethers from the various classes of acetals was as follows: cyclic acetals of cyclic ketones, 83-98percent; acyclic acetals of ketones, 72-94percent; acyclic and cyclic acetals of aldehydes, 65-90percent.
Reversibility of the Ring-opening Step in the Acid Hydrolysis of Cyclic Acetophenone Acetals
McClelland, Robert A.,Watada, Brian,Lew, Calvin S. Q.
, p. 1723 - 1728 (2007/10/02)
The acid-catalysed hydrolysis of the vinyl ethers α-(2-hydroxyethoxy)styrene 1a or α-(3-hydroxypropoxy)styrene 1b yields a mixture of acetophenone and a cyclic acetophenone acetal, 2-methyl-2-phenyl-1,3-dioxolane 3a or 2-methyl-2-phenyl-1,3-dioxane 3b.Ratios : have been determined by HPLC and by UV spectroscopy as 15 (from 1a) and 10 (from 1b).The acetals undergo further hydrolysis, but this is considerably slower than that of the vinyl ethers, and the above numbers represent products of kinetic control.These product ratios are equal to the rate constant ratios k2:k-1 for the partitioning of the oxocarbocations 1-(2-hydroxyethoxy)-1-phenylethyl 2a or 1-(3-hydroxypropoxy)-1-phenylethyl 2b between reaction with solvent water molecules and with the internal hydroxy group.These cations are also formed as intermediates in the hydrolysis of the cyclic acetals 3.That k2 is an order of magnitude greater than k-1 signifies that the rate-limiting step in this hydrolysis is the ring-opening forming the oxocarbocation, and that there is little reversibility in aqueous solutions.The hydrolysis reactions of these cyclic acetals are considerably slower than that of an acyclic analogue, the dimethyl acetal of acetophenone, by factors of 1.0 x 103 for 3a and 1.8 x 102 for 3b.This study demonstrates that these rate retardations cannot be accounted for by reversibility of the ring-opening step.The presence of the ring results in an inherent decrease in the rate constant for the H+-catalysed formation of the oxocarbocation.
