Natural kaolinitic clay: A remarkable reusable solid catalyst for the selective functional protection of aldehydes and ketones

Kaolin: A recyclable catalyst for the synthesis of 1,5‐benzodiazepines

“…Aluminosilicate clays are well characterized by their surface acidities, which render them efficient, versatile supports, or catalysts [21,22]. Although montmorillonite (bentonites) is widely used, kaolin-based reagents or kaolin-assisted reactions appear to be extremely limited [23][24][25]. Kaolin, owing to its acidic nature, can be a suitable replacement for various homogeneous acid catalysts.…”

“…Kaolin, owing to its acidic nature, can be a suitable replacement for various homogeneous acid catalysts. It has been used in the protection reaction of carbonyl compounds [23], alkylation of benzene [24], and bromination and chlorination of aromatic compounds [25].…”

Li–X-type zeolite mediated Michael addition of thiols to cyclic enones and its application in the synthesis of 13-thiaprostaglandins

“…On the contrary, zeolites afford cleaner Michael addition products with good yields [5]. Several organic transformations including oxidations [6], protection of aldehydes and ketones [7], Heck reaction [8], deprotection of allyl and cinnamyl esters [9], transthioacetalization [10], etc. using heterogeneous catalysts have been reported from our laboratory.…”

Silicotungstic Acid Modified Bentonite: An Efficient Catalyst for Synthesis of Acetal Derivatives of Aldehydes and Ketones

“…The protection of carbonyl functionality as an acetal or thioacetal derivative is a common practice in organic synthesis owing to their stability under mild acidic and basic conditions. They are generally obtained by the condensation of carbonyl compound with acetic anhydride [1], diols, dithiols and orthoformates [2][3][4][5], using Lewis acids as catalysts. A variety of catalysts are employed for this purpose like CoCl 2 [6], NiCl 2 [2], HCl [7], HClO 4 [8], sulfated zirconia [9] etc.…”