Résumé
The reactions of oxiranes R
FCH
2CH(–O–)CH
2 (R
F≡C
4F
9, C
6F
13, C
8F
17;
4a–
4c) with a series of alkanols in the presence of a Lewis acid took place at the terminal carbon atom with complete regioselectivity. 2-Hydroxyethyl methacrylate and acrylate reacted similarly. The reaction with alkane diols was controlled to proceed with one or two molecules of the oxiranes chemoselectively. Non-regioselective, base-catalysed ring opening by methacrylic acid (83% terminal attack) was discussed on the basis of the hard and soft acids and bases (HSAB) concept. A convenient transformation of the oxiranes to the corresponding diols
13a–
13c via dioxolane intermediates, and their conversion to bis-methacrylates, was accomplished with overall yields of 75%–79%. Thiourea converted the oxiranes into the corresponding thiiranes (
15a–
15c). The reactions afforded products generally in yields of 82%–98%.