ACCEPTED MANUSCRIPT
7
MHz, CDCl
3
)
δ
166.1, 131.9, 127.3, 109.7, 87.5, 81.7, 75.1, 54.4,
Isomer: 21% yield (0.02 g) as a yellow color oil. IR (neat)
1
4
.5; HRMS for C +Na calcd 173.0578; found 173.0580.
9
H
10
O
2
3000, 2929, 2838, 2221, 1639; H NMR (400 MHz, CDCl
3
)
δ
7.34-7.23 (m, 10H), 6.44 (d, J = 5.6 Hz, 1H), 6.13 (d, J = 5.6 Hz,
2
-Methoxy-5-(3-phenylprop-2-yn-1-ylidene)-2,5-
1H), 6.03 (s, 1H), 5.00 (s, 1H), 3.43 (s, 3H), 3.36 (s, 3H), 3.04 (s,
13
dihydrofuran (12b): DATA for Major Isomer: 55% yield
2H), 3.20 (d, J = 12.8 Hz, 2H), 2.81 (d, J = 12.8 Hz, 2H);
NMR (100 MHz, CDCl 166.4, 137.8, 131.9, 130.8, 127.7,
127.5, 126.3, 109.8, 93.3, 81.9, 81.4, 73.8, 58.3, 54.7, 43.2, 42.8;
HRMS for C25 +Na calcd 397.1780; found 397.1777.
C
(
0.059 g) as a yellow color oil. IR (neat) 3000, 2929, 2838, 2221,
3
) δ
1
1
7
1
639; H NMR (400 MHz, CDCl
3
) δ 7.48 (d, J = 7.2 Hz, 2H),
.33-7.28 (m, 3H), 6.42 (d, J = 5.6 Hz, 1H), 6.22 (d, J = 5.6 Hz,
26 3
H O
1
3
H), 6.17 (s, 1H), 4.91 (s, 1H), 3.52 (s, 3H); C NMR (100
165.0, 132.4, 131.3, 128.8, 128.1, 127.7, 123.9,
10.3, 94.5, 85.0, 80.5, 55.0; HRMS for C14 +Na calcd
35.0735; found 235.0737. Data for Minor Isomer: 32% yield
MHz, CDCl
1
2
3
)
δ
Acknowledgments
12 2
H O
We thank Prof. Martin E. Maier, Institute for Organic
Chemistry, University of Tuebingen, Germany for the helpful
discussions concerning the mechanism of the reaction. C. N.
thanks CSIR, New Delhi for a research fellowship.
(
0.03 g) as a yellow color oil. IR (neat) 3000, 2929, 2838, 2221,
1
1
7
1
639; H NMR (400 MHz, CDCl
.33-7.26 (m, 3H), 6.91 (d, J = 6.0 Hz, 1H), 6.28 (d, J = 6.0 Hz,
3
) δ 7.42 (d, J = 6.8 Hz, 2H),
1
3
H), 6.11 (s, 1H), 5.26 (s, 1H), 3.46 (s, 3H); C NMR (100
166.8, 132.9, 131.0, 128.2, 127.6, 127.4, 123.9,
MHz, CDCl
3
)
δ
References and notes
1
2
10.1, 91.6, 85.9, 81.4, 54.7; HRMS for C14
35.0735; found 235.0731.
H
12
O
2
+Na calcd
1
2
.
.
Heterocycles in Natural Products Synthesis Majumdar, K. C.;
Chattopadhyay, S. K (Eds); Wiley-VCH, Weinheim, 2011.
(a) Cuccarese, M. F., O’Doherty, G. A. In Asymmetric Synthesis
II: More Methods and Applications; Christmann, M.; Braese, S.
(Eds). Wiley−VCH: Weinheim, 2012 (b) Achmatowicz, O., Jr.;
Bukowski, P.; Szechner, B.; Zwierzchowska, Z.; Zamojski, A.
Tetrahedron 1971, 27, 1973-1996.
2
-(Hex-2-yn-1-ylidene)-5-methoxy-2,5-dihydrofuran
(12c):
DATA for Major Isomer: 68% yield (0.07 g) as a yellow color
oil. IR (neat) 3000, 2929, 2838, 2221, 1639; H NMR (400 MHz,
CDCl
1
3
)
δ
6.34 (d, J =5.2 Hz, 1H), 6.12 (d, J = 5.2 Hz, 1H), 6.11
3
.
(a) Piancatelli, G.; Scettri, A.; Barbadoro, S. Tetrahedron Lett.
(
s, 1H), 4.70 (s, 1H), 3.47 (s, 3H), 2.37 (td, J = 6.8, 1.6 Hz, 2H),
1
976, 17, 3555-3558. For a review, see: (b) Piutti, C.; Quartieri, F.
1
3
1
.63-1.55 (m, 2H), 1.01 (t, J = 7.2 Hz, 3H); C NMR (100 MHz,
164.2, 131.3, 128.8, 110.0, 95.6, 81.0, 75.5, 54.8, 22.2,
1.9, 13.5; HRMS for C11 +Na calcd 201.0891; found
01.0891. Data for Minor Isomer: 22% yield (0.02 g) as a
Molecules 2013, 18, 12290. For recent examples, see: (c) Veits, G.
K.; Wenz, D. R.; Read de Alaniz, J. Angew. Chem., Int. Ed. 2010,
3
CDCl ) δ
2
2
4
9, 9484. (d) Palmer, L. I.; Read de Alaniz, J. Angew. Chem., Int.
14 2
H O
Ed. 2011, 50, 7167. (c) Palmer, L. I.; Read de Alaniz, J. Org. Lett.
2013, 15, 476. (d) Wenz, D. R.; Read de Alaniz, J. Org. Lett.
1
yellow color oil. IR (neat) 3000, 2929, 2838, 2221, 1639; H
NMR (400 MHz, CDCl 6.78 (d, J = 5.6 Hz, 1H), 6.17 (d, J =
.6 Hz, 1H), 6.05 (s, 1H), 5.02 (s, 1H), 3.41 (s, 3H), 2.31 (td, J =
2
013, 15, 3250. (e) Yu, D.; Tahai, V. T.; Palmer, L. I.; Veits, G.
3
) δ
K.; Cook, J. E.; Read de Alaniz, J.; Hein, J. E. J. Org. Chem.
2013, 78, 12784. (f) Fisher, D.; Palmer, L. I.; Cook, J. E.; Davis, J.
E.; Read de Alaniz, J. Tetrahedron 2014, 70, 4105. (g) Lebœuf,
D.; Gandon, V.; Schulz, E. Org. Lett. 2014, 16, 6464-6467.
(a) Denisov, V. R.; Shevchenko, Z. A.; Khlebova, G. N.;
Alekseeva, E. M.; Favorskaya, I. A. J. Org. Chem. U.S.S.R. (Engl.
Transl.) 1984, 20, 2530-2533. (b) Gao, Y.; Wu, W. –L.; ; Ye, B.;
Zhou, R.; Wu, Y. –L. Tetrahedron Lett, 1996, 37, 893-896. (c)
Gao, Y.; Wu, W. –L.; ; Ye, B.; Wu, Y. –L.; Zhou, R. Tetrahedron,
5
7
1
3
.2, 1.2 Hz, 2H), 1.61-1.53 (m, 2H), 1.00 (t, J = 7.2 Hz, 3H);
166.0, 131.9, 127.4, 109.7, 92.1,
1.8, 76.1, 54.4, 22.4, 21.6, 13.5; HRMS for C11 +Na calcd
01.0891; found 201.0891.
C
NMR (100 MHz, CDCl3)
8
2
δ
4
5
.
.
14 2
H O
2
-(5-(Benzyloxy)pent-2-yn-1-ylidene)-5-methoxy-2,5-
1
998, 54, 12523-12538.
(a) Dhiman, S.; Ramasastry, S. S. V. Org. Biomol. Chem. 2013,
1, 4299-4303. (b) Dhiman, S.; Ramasastry, S. S. V. Indian J.
dihydrofuran (12d): DATA for Major Isomer: 60% yield
(
0.06 g) as a yellow color oil. IR (neat) 3000, 2929, 2838, 2221,
1
1
1
639; H NMR (400 MHz, CDCl
J = 5.6, 1H), 6.15 (d, J = 5.6, 1H), 6.12 (s, 1H), 4.66 (s, 1H), 4.58
s, 2H), 3.65 (t, J = 7.2, 2H), 3.46 (s, 3H), 2.73 (t, J = 7.2, 2H);
3
)
δ
7.37-7.25 (m, 5H), 6.35 (d,
Chem., Sect. A 2013, 52, 1103. (c) Dhiman, S.; Ramasastry, S. S.
V. J. Org. Chem. 2013, 78, 10427−10436.
(a) Prasad, K. R.; Nagaraju, C. Org. Lett., 2013, 15, 2778-2781.
(b) Nagaraju, C.; Prasad, K. R. Angew. Chem., Int. Ed. 2014, 53,
6
7
.
.
(
1
3
C NMR (100 MHz, CDCl3)
27.6, 127.5, 110.1, 91.8, 80.6, 76.5, 72.8, 68.5, 54.7, 21.3;
HRMS for C H O +Na calcd 293.1154; found 293.1158. Data
δ 164.6, 138.1, 131.7, 128.8, 128.3,
1
0997-11000.
1
For strategy of oxidative ring opening of furan to the
a
1
7
18
3
corresponding E-but-2-en-1,4-dione in natural product synthesis
see: (a) Kobayashi, Y; Nakano, M; Kumar, G. B; Kishihara, K. J.
Org. Chem. 1998, 63, 7505-7515. (b) Prasad, K. R; Pawar, A. B.
Org. Lett. 2011, 13, 4252-4255. (c) Prasad, K. R.; Revu. O. J.
Org. Chem. 2014, 79, 1461−1466. For acid mediated ring opening
of 2,5-di substituted furans to the corresponding 1,4-diones see:
(d) Büchi, G.; Wüest, H. J. Org. Chem. 1966, 31, 977–978. (e)
Waidmann, C. R.; Pierpont, A. W.;Batista, E. R.; John C. Gordon,
J. C.; Martin, R. L.; Silks, L. A. P.; West, R. M.; Wu, R. Catal.
Sci. Technol., 2013, 3, 106-115.
The reported synthesis for saturated γ-keto esters from furans
involve the initial oxidation of furans to the 2,5-dialkoxy furans
followed by reaction with ruthenium hydride or TMSI. (a) Hirai,
K., Suzuki, H., Kashiwagi, H., Moro-oka, Y.; Ikawa, T. Chem.
Lett, 1982, 23 (b) Feringa, B. L.; Dannenberg, W. Tetrahedron
Lett, 1983, 13, 509-514. Feringa and Dannenberg also reported a
procedure involving the conversion of furans to γ-
methoxybutyrolactone and subsequent reduction/esterification
sequence.
for Minor Isomer: 20% yield (0.02 g) as a yellow color oil. IR
1
(
neat) 3000, 2929, 2838, 2221, 1639; H NMR (400 MHz,
CDCl 7.36-7.26 (m, 5H), 6.77 (d, J = 5.6 Hz, 1H), 6.18 (d, J
5.6 Hz, 1H), 6.05 (s, 1H), 5.01 (s, 1H), 4.57 (s, 2H), 3.62 (t, J =
3
) δ
=
1
3
6
.8 Hz, 2H), 3.42 (s, 3H), 2.66 (t, J = 6.8 Hz, 2H); C NMR (100
MHz, CDCl 166.5, 138.1, 132.2, 128.4, 127.7, 127.6, 127.4,
09.8, 88.5, 81.4, 77.2, 72.9, 68.6, 54.5, 21.1; HRMS for
+Na calcd 293.1154; found 293.1158.
3
) δ
1
17 18 3
C H O
8
.
2
2
-(4,4-Dibenzyl-5-methoxypent-2-yn-1-ylidene)-5-methoxy-
,5-dihydrofuran (12e): Data for Major Isomer: 64% yield
(
0.07 g) as a yellow color oil. IR (neat) 3000, 2929, 2838, 2221,
1
1
7
1
2
1
8
3
639; H NMR (400 MHz, CDCl ) δ 7.45 (d, J = 7.2 Hz, 4H),
.34-7.24 (m, 6H), 6.36 (d, J = 5.6 Hz, 1H), 6.18 (s, 2H), 4.65 (s,
H), 3.54 (s, 3H), 3.35 (s, 3H), 3.04 (d, J = 12.8 Hz, 2H), 3.04 (s,
1
3
9
.
The crystallographic data has been deposited with the Cambridge
Crystallographic Data Center. CCDC No. 1027186 contains the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
3
H), 2.88 (d, J = 12.8 Hz, 2H); C NMR (100 MHz, CDCl ) δ
64.8, 137.8, 131.6, 130.9, 129.0, 127.6, 126.2, 110.0, 96.6, 81.1,
0.7, 73.6, 58.3, 54.7, 43.2, 42.83, 42.79; HRMS for
25 26 3
C H O +Na calcd 397.1780; found 397.1777. Data for Minor