A Facile, Catalytic, and Environmentally
Benign Method for Selective Deprotection
of tert-Butyldimethylsilyl Ether Mediated
by Phosphomolybdic Acid Supported on
Silica Gel
than typical solid acids. Acidic or neutral substances such
as silica gel, active carbon, and acidic ion-exchange resin
are suitable supports, the most often used being silica
gel. Phosphomolybdic acid supported on silica gel (PMA/
2
SiO ) is found to be an excellent catalyst for vapor-phase
6
organic reactions, and most of the processes have already
7
been commercialized. However, the synthetic potential
G. D. Kishore Kumar and Sundarababu Baskaran*
of PMA/SiO
explored fully.
2
8in liquid-phase reactions is yet to be
Department of Chemistry, Indian Institute of Technology
Madras, Chennai 600 036, India
The TBDMS (tert-butyldimethylsilyl) ether has become
one of the most popular silyl protective groups used in
organic synthesis.9 It is easily introduced as well as
1
0
readily removed under a variety of conditions. A vast
array of acidic, neutral, basic, reducing, oxidizing, and
fluoride-based reagents have been reported for the re-
moval of the TBDMS group.11 However, most of these
deprotection methods require hazardous reagents and
aqueous workup procedures that are detrimental to the
environment, and perhaps least attractive is that in
nearly all cases the reagent cannot be recovered and
recycled. These limitations prompted us to investigate
an environmentally benign reagent that can catalyze the
cleavage of TBDMS ether under very mild conditions.
Received February 10, 2005
An environmentally benign PMA supported on SiO2 is found
to be an efficient catalyst for the chemoselective deprotection
of TBDMS ethers under very mild conditions. Various labile
functional groups such as isopropylidene acetal, OTBDPS,
OTHP, Oallyl, OBn, alkene, alkyne, OAc, OBz, N-Boc,
N-Cbz, N-Fmoc, mesylate, and azide are found to be stable
under the reaction conditions. This “truly catalytic” hetero-
geneous reaction does not require aqueous workup, and the
supported catalyst and the solvent can be readily recovered
and recycled.
12
Our continued interest in exploring the synthetic
potential of heteropoly acid as a novel green catalyst has
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10.1021/jo0502697 CCC: $30.25 © 2005 American Chemical Society
4520
J. Org. Chem. 2005, 70, 4520-4523
Published on Web 04/12/2005