Facile catalyzed acylation of alcohols, phenols, amines and thiols based on ZrOCl 2 Æ8H 2 O and acetyl chloride in solution and in solvent-free conditions Rina Ghosh, * Swarupananda Maiti and Arijit Chakraborty Department of Chemistry, Jadavpur University, Kolkata 700 032, India Received 25 August 2004; revised 19 October 2004; accepted 28 October 2004 Available online 21 November 2004 Abstract—Acylation of heteroatoms (O, N and S) with acetyl chloride based on the use of a catalytic amount of the moisture stable, inexpensive ZrOCl 2 Æ8H 2 O, proceeds efficiently producing the corresponding acylated products in excellent yields. Ó 2004 Elsevier Ltd. All rights reserved. Acetylation of hydroxy groups is an often used protec- tion technique because of the ease of formation as well as mild conditions for deprotection. 1 Such acylations can be effected with acetic anhydride or acetyl chloride in the presence of bases like pyridine, 1 Et 3 N, 1 DMAP, 2 Bu 3 P, 3 etc. Acylations with acids, 4 acyl imidazoles 5 and acyl urea 6 are also known. Acid catalyzed acyl- ations mainly use Brønsted acids 7 including polymeric acids 8 or Lewis acids. Metal chlorides, 9 metal tri- flates 4a,10 and metal perchlorates 11 have been utilized as Lewis acids for acetylation of heteroatoms. Recently, other reagents such as, I 2 , 12 La(O i Pr) 3 , 13 vanadyl(V) ace- tate, 14 distannoxane, 15 ionic liquids, 16 twisted amides, 17 solid supported reagents 18,19 or lipase enzymes 18 have also been employed for the same purpose. However, quite a few of the reported methods have limitations mainly in respect of stability, cost, availability, load and reusability of the catalyst or in terms of yields, cum- bersome methodologies, flammability or risk of explo- sion of the reagents. Thus, the search for new reagents and methods is still of practical importance. Due to their easy availability 20 and low toxicity 21 Zr(IV) salts have recently attracted much attention. 22 This has been reflected in their application, especially ZrCl 4 , in several organic transformations. 4b,9e,23 Very recently, Chakraborty and co-workers reported ZrCl 4 catalyzed acetylations of heteroatoms by acetic anhydride. 9e There have been only a few reports on the metal oxysalt-based organic reactions. 11b,24 In continuation of our system- atic evaluation of the efficacy of metal salts/oxysalts as catalysts 25 or procatalysts, 24c we report, herein, our results on acetylations of alcohols, phenols, aliphatic and aromatic amines, a thiol and a thiophenol with acetyl chloride using a catalytic amount of ZrOCl 2 Æ8H 2 O(Scheme 1, Tables 1 and 2). 26,27 To the best of our knowledge, this is the first demonstration of the ZrOCl 2 Æ8H 2 O based acetylation. ZrOCl 2 Æ8H 2 O is a moisture stable, readily available and inexpensive oxysalt of Zr and thus its handling is easier in compar- ison to that of the moisture sensitive ZrCl 4 . 0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2004.10.164 Keywords: Acylation; Catalyzed; ZrOCl 2 Æ8H 2 O; Acetyl chloride. * Corresponding author. E-mail: ghoshrina@yahoo.com RXH MeCOCl, neat or CH 2 Cl 2 ZrOCl 2 .8H 2 O (0.1-0.5 mol%) RXCOMe X=O/NH/S R=aliphatic/aromatic (a) (b) Scheme 1. Table 1. Acetylation of b-naphthol based on ZrOCl 2 Æ8H 2 O(x mol %) and AcCl (2 equiv) in different solvents at room temperature Entry Mol % Solvent Time Yield (%) 1 0.5 CH 3 CN 1h 91 2 0.5 THF 12h 53 3 0.5 PhCH 3 12h 85 4 0.1 CH 2 Cl 2 2.5 h 85 5 0.5 CH 2 Cl 2 45 min 95 6 2 CH 2 Cl 2 30 min 97 Tetrahedron Letters 46 (2005) 147–151 Tetrahedron Letters