Page 7 of 46
Journal Name
Pleas Ge rdeo e nn o Ct ah de j mu si ts mt r ya rgins
DOI: 10.1039/C5GC01785H
COMMUNICATION
Experimental
General procedure for the deprotection of THP/MOM/Ac/Ts
ethers and concomitant oxidative dehydrogenation of alcohols
(
15a-28a). To a solution of alcohol (15-28) in water (2 mL) and 3-4
drops of acetone was added to an aqueous solution of β-
cyclodextrin (1 mmol in 10 mL of water) at 60 °C and allowed to
cool to room temperature. Then, IBX (1.5 equiv. per alcohol or C-C
Fig.
deprotection of phenolic ether and concomitant oxidative cleavage heated to 60 °C, and the reaction was constantly monitored by TLC
of chalcone epoxide. until complete consumption of starting material was observed. The
plausible mechanism for detetrahdropyranylation and reaction mixture was cooled to room temperature and extracted
concomitant oxidative cleavage of chalcone epoxide is proposed in with EtOAc (3 × 15 mL). The organic layer was washed with 5% aq.
Scheme 1. The role of β-CD appears to be not only to activate the NaHCO and dried over anhydrous Na SO and concentrated in a
1 Mechanistic Rationale of β-cyclodextrin/IBX induced bond to be oxidized) was added while stirring. The mixture was
A
3
2
4
THP ether and epoxide by hydrogen bonding but also to promote vacuo. The crude product was purified by silica gel column
highly regioselective ring opening due to inclusion complex chromatography using hexane/ethyl acetate (8:2) as an eluent if
formation and thereby facilitating the hydrolysis. Since the β-CD required otherwise compounds were pure enough for the spectral
cavity is hydrophobic in nature it may also be forming reversible elucidation.
complexes with the THP ethers. In these reactions, Cyclodextrin can General procedure for the deprotection of THP/MOM/Ac/Ts
be recycled and reused, also the iodosobenzoic acid (IBA) obtained ethers (29a-38a). β-cyclodextrin (0.1 mmol) was dissolved in water
o
during the reaction can be converted again to IBX by oxidation [11].
(25 ml) at 60 C; THP/MOM/Ac/Ts ether (1 mmol) in water: acetone
mixture (2 ml: 3-4 drops) was added slowly with stirring. The stirring
o
was continued at 60 C for the specified time (Table 5). Then the
reaction mixture was cooled to room temperature and extracted
with EtOAc (3 × 15 mL), dried over anhydrous Na SO and the
2 4
solvent was removed in vacuo. The crude product was purified by
silica gel column chromatography using hexane/ethyl acetate (9:1)
as eluent if required otherwise compounds were pure enough for
the spectral elucidation.
Acknowledgements
The authors wish to express their gratitude to the BRNS, India
for financial support, DST, New Delhi for providing HRMS
facility and CSIR, New Delhi for awarding SRF to S.K.
Notes and references
1
2
3
(a) V. Amaranth, A. D. Broom, Chem. Rev. 1977, 77, 183; (b)
D. N. Robertson, J. Org. Chem. 1960, 25, 931.
A. R. Hajipour, M. Kargosha, A. E. Ruoho, Synth. Commun.
Scheme 1. Plausible reaction mechanism of β-cyclodextrin/IBX
induced deprotection of phenolic ether and concomitant oxidative
cleavage of chalcone epoxide.
2
009, 39, 1084.
(a) B. Tamami, K. Parvanak, Tetrahedron Lett. 2004, 45, 715;
b) V. V. Namboodiri, R. S. Varma, Tetrahedron Lett., 2002,
, 1143; (c) B. S. Babu, K. Balasubramanian, Tetrahedron
(
4
3
Conclusions
Lett. 1998, 39, 9287; (d) P. N. Reddy, B. K. Sunil, P. S. Kumar,
N. Y. Srinivasulu, T. Reddy, B. Rajitha, Chem. Heterocycl.
Compd. 2005, 41, 11; (e) R. R. Diaz, C. R. Melgarejo, M. T.
Plaza, I. I. Cubero, J. Org. Chem. 1994, 59, 7928; (f) M.
Narender, M. S. Reddy, K. R. Rao, Synthesis, 2004, 30, 1741;
In summary, we have presented an elegant and simple
methodology for one pot deprotection of MOM/THP/Ac/Ts
ethers and concomitant oxidative cleavage of chalcone
epoxides and oxidative dehydrogenation of alcohols employing
a mild and eco-friendly oxidizing agent β-CD/IBX in water
under supramolecular catalysis. Thus, we have demonstrated
for the first time the synthesis of highly valuable synthons β-
hydroxy 1, 2 diketones, 1, 2, 3 triketones and α, β-unsaturated
ketones directly from the easily accessible chalcone epoxides
and 1, 3 diphenyl alcohols in the presence of β-CD/IBX in
water. β-CD was found indispensable for the deprotection
reaction. To the best of our knowledge, this is the first report
of deprotection with sequel transformations to form β-
hydroxy 1, 2 diketones, 1, 2, 3 triketones and α, β-unsaturated
ketones in aqueous medium and therefore represents a novel
methodology. It is an economical and user-friendly protocol.
(g) C. Wiles, P. Watts, S. Haswell, Tetrahedron Lett. 2005, 61,
209; (h) B. S. Babu, K. K. Balasubramanian, Tetrahedron
5
Lett. 1998, 39, 9287; (i) B. Karimi, J. Maleski, Tetrahedron
Lett. 2002, 43, 5353; (j) B. C. Ranu, M. Saha, J. Org. Chem.
1
7
994, 59, 8269; (k) T. Mineno, Tetrahedron Lett., 2002, 43,
975; (l) G. G. Haraldsson, J. E. Baldwin, Tetrahedron, 1997,
53, 215; (m) K. Tanemura, T. Haraguchi, T. Suzuki, Bull. Chem.
Soc. Jpn. 1992, 65, 304; (n) H. M. S. Kumar, B. V. S. Reddy, E.
J. Reddy, J. S. Yadav, Chem. Lett., 1999, 28, 857; (o) J. S.
Yadav, D. Srinivas, G. S. Reddy, Synth. Commun. 1998, 28
,
1
8
399; (p) A. T. B. Molnarand, Tetrahedron Lett. 1996, 37
597.
,
4
(a) S. Amano, N. Takemura, M. Ohtsuka, S. Ogawa, N. Chida,
Tetrahedron, 1999, 55, 3855; (b) G. V. M. Sharma, K. L.
Reddy, P. S. Lakshmi, P. R. Krishna, Tetrahedron Lett. 2004,
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins