TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 385–387
A mild procedure for the clay catalyzed selective removal of the
tert-butoxycarbonyl protecting group from aromatic amines
Nadim S. Shaikh, Anil S. Gajare, Vishnu H. Deshpande ∗ and Ashutosh V. Bedekar ∗
Division of Organic Chemistry: Technology, National Chemical Laboratory, Pune 411 008, India
Received 3 September 1999; accepted 26 October 1999
Abstract
The application of solid acidic catalysts for the selective removal of N-Boc protection is presented in this report.
Montmorillonite K10 was found to be an effective catalyst in removing aromatic N-Boc groups while leaving
aliphatic N-Boc amines untouched. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: clay catalysts; N-tert-butoxycarbonyl amines; deprotection.
The tert-butoxycarbonyl group (Boc) is frequently used as a protecting group for 1° and 2° amines1
and amino acids in peptide chemistry2 due to its stability to mildly acidic as well as basic conditions.
A number of reagents have been known3 to effect clean removal of this protecting group, most under
homogeneous conditions. The only example known of this cleavage using solid reagents is the use of
silica gel under reduced pressure.4 Developing new applications for heterogeneous catalysts for organic
transformations has been a subject of ongoing research in our laboratory.5 Recently there has been an
upsurge in new applications of clays as catalysts for several organic reactions.6 We wish to report in this
communication a preliminary account of the use of acidic clays as catalysts for the selective removal of
the N-Boc group.
A mixture of the N-Boc aromatic amine and kaolinitic clay (KC)7 or commercial montmorillonite K10
(20% w/w) was refluxed in dichloroethane to afford the deprotected amine in excellent yield (Scheme 1).
Scheme 1.
A series of N-Boc amines were subjected to the deprotection conditions with different catalysts and
the results are presented in Table 1. The recoverability and reusability of each catalyst was tested by the
∗
Corresponding authors. Fax: +91 020 5893614.
0040-4039/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
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