An Efficient and Chemoselective Procedure for Acylal Synthesis
A novel heterogeneous efficient procedure has been developed for the chemoselective synthesis of acylals (1,1-diacetates) under solvent-free conditions. A novel catalyst prepared by the sulfuric acid catalyzed copolymerization of p-toluenesulfonic acid and paraformaldehyde displays extremely high activities for the title reactions, affording average yields over 90% within several minutes. A comparative study showed that the novel catalyst has much higher activity than other catalysts used for this purpose. Besides, the novel catalyst displays chemoselectivity for the protection of aldehydes in the presence of ketones. In addition the high acidity (4.0 mmol/g), thermal stability (200 ºC) and easy reusability make the novel catalyst one of the best choices for the process.
Metal-based Lewis acid catalysts for conversion of a variety of aldehydes with acetic anhydride to gem 1,1-diacetates
Selective protection of carbonyl groups such as oxathioacetals, acylals, acetals and dithioacetals is the vital steps in organic chemistry. Among these groups, protection of aldehydes such as diacetates (acylals) has attracted more attention in the organic chemistry due to its superior applications such as commodity chemical in various fields of chemistry, their ease of preparation and their stability toward basic and neutral conditions. Beyond their protecting role, 1,1-diacetates are important precursors for the synthesis of acetoxydienes, starting materials as valuable intermediates for Diels–Alder cycloaddition reactions and neutral and basic media. Also acylals have been used as intermediates in industry as cross-linking agents for cellulose in cotton. Protection of carbonyl group of aldehydes by acetic anhydride in the presence of acid catalyst is the most convenient way. This review precises chemoselective procedure for the preparation of acylals by using the metal-based Lewis acid catalysts, magnetic nanocatalysts, ionic liquids, strong protic acid and solid acids.
The chromosomes of Chrysanthemum,
NEW varieties of the garden chrysanthemum arise primarily from seed. They are propagated vegetatively and many give rise to bud sports in sequence and in parallel to give whole families of varieties. The original sports would naturally be chimras and it is not surprising therefore that they often revert to the previous type. Whereas some varieties sport continually from the time of their origin, others remain stable for many years. Those considered in this account do, mostly, sport freely. Since varieties may remain stable for a considerable number of years and then suddenly sport it is probable that all varieties possess the ability to sport. The origin of bud sports is unpredictable. Some confusion in naming has arisen as the same or similar sports have occurred and been propagated in different places under different names. Consequently there are, for example, several forms similar to, but not identical with, the original Favourite Supreme raised by Messrs A. G. Vinten. It might well be that each individual variety would be better termed a sub-family to include all its minor variants. The different Chrysanthemum sports are described in scattered numbers of the R.H.S. Journal—more particularly, for the Favourite family, in Vol. 63, 1938, pp. 139-141. The object of this study is to discover the cause of sporting.