Zinc Chloride as an Efficient Catalyst for Chemoselective Dimethyl Acetalization

The use of anhydrous CeCl3 as a recyclable and selective catalyst for the acetalization of aldehydes and ketones

“…A greener, atom efficient approach to acetals is the use of trialkyl orthoesters instead of alcohols, because they provide both alkoxy groups while scavenging the water produced in the reaction. 3,4,9,10,13,14 In view of our interest in the development of new, cleaner methods for classical reactions 22 and new applications of cerium(III) in organic synthesis, 23 we decide to study the reaction of carbonyl compounds 1 with trimethyl orthoformate to obtain dimethyl acetals 2 (Tables 1 and 2). …”

“…2 Because of the versatility and usefulness of acetals in organic synthesis, several methods for the protection [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and the selective, mild deprotection 21 of aldehydes and ketones have been described. The classical procedure for protection involves the Lewis [3][4][5][6][7][8][9][10][11][12][13][14][15] or protic acid-catalyzed [16][17][18][19][20] reaction of a carbonyl compound with a large excess of an alcohol in the presence of a water scavenger. Among the employed Lewis acids are metal triflates, [3][4][5][6][7][8] 19 and silica-supported HClO 4 20 have been used as protic acids.…”

Synthesis, structural determination and antimicrobial evaluation of two novel CoII and ZnII halogenometallates as efficient catalysts for the acetalization reaction of aldehydes

“…Therefore, the development of new catalytic structures to successfully perform this protection is of high interest for the progress of this field. Despite the number of reported works regarding this reaction, to the best of our knowledge the use of Co- [57, 58] and Zn-based catalysts [59, 60] has been less explored in the literature until now. In this spectrum of properties, we envisioned the possibility of testing the effectiveness of our metallic species in the acetalization reaction of aldehydes as a benchmark process.…”

Applications of alkyl orthoesters as valuable substrates in organic transformations, focusing on reaction media

“…In 2003, Ma et al presented an efficient and chemoselective method for the preparation of diethyl acetals in good to excellent yields (63-96%) via the acetalization 178,[396][397][398][399][400][401][402][403][404][405][406][407][408] of aldehydes/ ketones with TEOF using TiO 2 /SO 4 2À in reuxing ethanol for 25 min to 3 h. It was found that, in competitive reactions, aldehydes and cyclic aliphatic ketones revealed excellent chemoselectivity. 408 The reaction of enamines (470) with trialkyl orthoformates (4,5) was also accomplished in the presence of BF 3 $OEt 2 in CH 2 Cl 2 to give a-dialkoxymethyl carbonyl compounds (471), aer hydrolysis, in 61-85% yields within 1 h (Scheme 138).…”