Pergamon Tetrahedron Letters 40 (1999) 5613-5616 I TETRAHEDRON LETTERS Remarkable Deprotection of THP and THF Ethers Catalysed by Cerium Ammonium Nitrate (CAN) Under Neutral Conditions IStV~ E Mark6*, Ali Ates, Benoit Augustyns, Arnaud Gautier, Yannick Quesnel, Laurent Turet and Marianne Wiaux Universit6 catholique de Louvain, Ddpartement de Chimie, Laboratoire de Chimie Organique, B'~timent Lavoisier, Place Louis Pasteur 1, B-1348, Louvain-la-Neuve, Belgium. Received 1 April 1999; accepted 25 May 1999 Abstract: The catalytic deprotection of a range of functionalised THP and THF ethers can be efficiently performed, under neutral conditions, using as little as 3 tool% CAN in MeCN/borate buffer (pH = 8). © 1999 ElsevierScienceLtd. All rights reserved. The protection-deprotection of alcohol functionalities is of paramount importance in organic chemistry, as testified by the plethora of imaginative reagents and methods that have been devised to accomplish this key functional group interconversion.l The amount of work dedicated to this area is hardly surprising since, more often than not, the success of a total synthesis endeavour crucially depends upon the compatibility and selective unravelling of carefully chosen protecting groups. Amongst the wealth of reagents typically employed to shelter a hydroxyl function, the tetrahydropyranyl- (THP) and tetrahydrofuranyl- (THF) ethers still occupy a prominent position.1 However, their removal usually entails rather harsh acidic conditions which are rarely compatible with sensitive substrates. 2 3 mol% CAN R1 l~ n 20 - 60°C R1 R'~'O f~O MeCN / borate ~ R~J"O "H 1 buffer (pH = 8) 2 In=l, 2; R, R1 = alkyl, ary,, H.} Figure1 In a preceding communication, we have reported that cerium ammonium nitrate (CAN) was an effective reagent for the unmasking of ketones and aldehydes from the corresponding ketals and acetals under mild conditions) Unfortunately, the large amounts of CAN required in this early protocol (2.5 eq) provided a serious impediment to its use on large scale. In order to 'alleviate this limitation, we have explored catalytic versions of this unusual deprotection technique 4 and discovered that minute quantities of CAN (3 tool%), in the presence of a borate buffer (pH = 8), smoothly and efficiently unravelled a range of acetals and ketals. 5. 6 In this Article, we wish to disclose the results of our investigations in the application of this novel, CAN- catalysed protocol, for the removal of THP and THF protecting groups, under neutral conditions (Figure l). 0040-4039/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PH: S0040-4039(99)01043-6