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M. Adachi et al.
LETTER
(6) The similar cyclic methylene acetal formation in
deprotection of MTM was reported: Wachter, M. P.; Adams,
R. E. Synth. Commun. 1980, 10, 111.
(7) For reviews of Pummerer rearrangement, see: (a) DeLucchi,
O.; Miotti, U.; Modena, G. In Organic Reactions; Paquette,
L. A., Ed.; John Wiley: New York, 1991, Chap. 3, 157–184.
(b) Grieson, D. S.; Husson, H. P. In Comprehensive Organic
Synthesis; Vol. 6; Trost, B. M., Ed.; Pargamon: Oxford,
1991, 909–947. (c) Bur, S. K.; Padwa, A. Chem. Rev. 2004,
104, 2401.
directly poured into an aq ammonia, resulting in exclusive
formation of 12. For details, see the Supporting Information.
(11) TLC analysis indicated that the primary alcohol of 9 was
first acetylated and then acetylation of the sulfoxide
occurred to a mixture of the product 10a and 10b.
(12) The related reactions involving oxonium intermediates
generated from the sulfoxides of S,O-thioacetals with Tf2O
or TFAA, and subsequent transformation were reported. For
examples, see: (a) Kahne, D.; Walker, S.; Cheng, Y.; Van
Engen, D. J. Am. Chem. Soc. 1989, 111, 6881. (b) Tanaka,
H.; Chino, A.; Takahashi, T. Tetrahedron Lett. 2012, 53,
2493.
(8) The model compound 8 was prepared from D-pinene through
diol 12 in two steps. For details, see the Supporting
Information.
(13) As it turned out later, the similar reactions giving acetoxy
sulfides from the sulfoxides of MTM were reported:
Antonsen, Q.; Benneche, T.; Undheim, K. Acta Chem.
Scand., Ser. B 1988, 42, 515.
(9) 1H NMR Data of Acetoxy Sulfide 10a and Acetoxy Acetal
10b (ca. 1:4.6 Inseparable Mixture)
1H NMR (300 MHz, CDCl3): δ = 0.96 (3 H, s, CH3), 1.26 (3
H, s, CH3), 1.40–1.52 (1 H, m), 1.80–1.98 (5 H, m), 2.02 (3
H, s, CH3 of Ac), 2.08 (3 H, s, CH3 of Ac), 2.13–2.24 (2 H,
m), 4.12 (0.18 H, d, J = 12 Hz, CCHAHBOAc of acetoxy
sulfide), 4.14 (1.64 H, s, CCH2OAc of acetoxy acetal), 4.22
(0.18 H, d, J = 12 Hz, CCHAHBOAc of acetoxy sulfide), 4.50
(0.18 H, d, J = 10 Hz, OCHAHBS), 4.64 (0.18 H, d, J = 10 Hz,
OCHAHBS), 5.22 (0.82 H, d, J = 7 Hz, OCHAHBOAc), 5.24
(0.36 H, s, SCH2OAc), 5.35 (0.82 H, d, J = 7 Hz,
OCHAHBOAc).
(14) For details regarding preparation of the substrates, see the
Supporting Information.
(15) 1H NMR Data of the Trifluoroacetoxy Acetal Derived
from 16
1H NMR (300 MHz, CDCl3): δ = 0.19 (9 H, s, CH3 of TMS),
0.83 (3 H, s, CH3), 0.84–2.42 (18 H, m), 1.02 (3 H, s, CH3),
3.37 (3 H, s, CH3OCH2O), 5.26 (1 H, br d, J = 5 Hz, C=CH),
5.76 (1 H, d, J = 6 Hz, OCHAHBOTFA), 5.84 (1 H, d, J = 6
Hz, OCHAHBOTFA).
(10) 1H NMR spectra of the crude products of the Pummerer
reaction indicated the presence of cyclic methylene acetal
13, which might be formed from 11a and/or 11b during the
workup (concentration). Therefore, the reaction mixture was
(16) The structure of 21 was identified by analysis of NMR and
MS spectra. For details, see the Supporting Information.
(17) The mechanism of formation for 20 is unclear.
(18) Ueda, M. Chem. Lett. 2012, 41, 658.
Synlett 2014, 25, 2498–2502
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