P.D. Dharpure et al. / Tetrahedron Letters xxx (xxxx) xxx
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yellow solid (83%, 25.5 mg); mp 41–42 °C; eluent (petroleum
ether/ethyl acetate = 7:3); Rf = 0.4; 1H NMR (400 MHz, CDCl3): d
10.41 (s, 1H), 8.13–8.08 (m, 1H), 7.96–7.92 (m, 1H), 7.82–7.73
(m, 2H); 13C NMR (100 MHz, CDCl3): d 188.26, 149.69, 134.20,
133.83, 131.46, 129.74, 124.61; HRMS (ESI TOF) m/z calcd for
C7H6NO3 [M+H]+ 152.0348, found 152.0347.
Thiophene-2-carbaldehyde (2r): Compound 2r was synthesized
following the general procedure B. Compound 2r was obtained as
brown oil (87%, 19.5 mg); eluent (petroleum ether/ethyl acet-
ate = 9:1): Rf = 0.5; 1H NMR (400 MHz, CDCl3): d 9.93 (s, 1H),
7.78–7.75 (m, 2H), 7.22–7.19 (m, 1H); 13C NMR (100 MHz, CDCl3):
d 183.1, 144.1, 136.4, 135.2, 128.4; HRMS (ESI TOF) m/z calcd for
C5H5OS [M+H]+ 113.0061, found 113.0070.
1H-pyrrole-2-carbaldehyde (2s): Compound 2s was synthesized
following the general procedure B. Compound 2s was obtained as
white solid (89%, 16.9 mg); mp 39–43 °C; eluent (petroleum
ether/ethyl acetate = 8:2); Rf = 0.4; 1H NMR (400 MHz, CDCl3): d
11.24 (s, 1H), 9.48 (s, 1H), 7.18 (s, 1H), 7(s, 1H), 6.31 (s, 1H); 13C
NMR (100 MHz, CDCl3) d102.7, 55.7, 50.6, 45.4, 34.3; HRMS (ESI
TOF) m/z calcd for C5H6NO [M+H]+ 96.0449, found 96.0450.
Furan-2-carbaldehyde (2t): Compound 2t was synthesized fol-
lowing the general procedure B. Compound 2t was obtained as yel-
low oil (82%, 15.7 mg); eluent (petroleum ether/ethyl
acetate = 19:1); Rf = 0.5; 1H NMR (400 MHz, CDCl3): d 9.67 (s,
1H), 7.72–7.68 (m, 1H), 7.27 (dd, J = 3.6, 0.8 Hz, 1H), 6.62 (dd,
J = 3.6, 1.7 Hz, 1H); 13C NMR (100 MHz, CDCl3): d 177.80, 152.84,
148.09, 121.26, 112.57; HRMS (ESI TOF) m/z calcd for C5H5O2 [M
+H]+ 97.0290, found 97.0289.
120.4; HRMS (ESI TOF) m/z calcd for C13H9O [M]+ 181.0653, found
181.0658.
4-phenylbut-3-yn-2-one (2z): Compound 2z was synthesized
following the general procedure B. Compound 2z was obtained as
colourless oil (97%, 28 mg); eluent (petroleum ether/ethyl acet-
ate = 9:1); Rf = 0.45; 1H NMR (400 MHz, CDCl3): d 7.59–7.55 (m,
2H), 7.48–7.43 (m, 1H), 7.40–7.36 (m, 2H), 2.45 (s, 3H); 13C NMR
(100 MHz, CDCl3): d 184.7, 133.1, 130.8, 128.7, 120, 90.4, 88.4,
32.9; HRMS (ESI TOF) m/z calcd for C10H9O [M+H]+ 145.0653, found
145.0657.
(E)-3-(2-methoxyphenyl)acrylaldehyde (2aa): Compound 2aa
was synthesized following the general procedure B. Compound
2aa was obtained as white solid (92%, 29.8 mg); mp 42–45 °C; elu-
ent (petroleum ether/ethyl acetate = 15:5); Rf = 0.5; 1H NMR
(400 MHz, CDCl3) d 9.69 (d, J = 7.9 Hz, 1H), 7.84 (d, J = 16.1 Hz,
1H), 7.55 (dd, J = 7.7, 1.7 Hz, 1H), 7.41 (ddd, J = 8.8, 7.5, 1.7 Hz,
1H), 7.03–6.98 (m, 1H), 6.95 (d, J = 8.4 Hz, 1H), 6.79 (dd, J = 16.1,
7.9 Hz, 1H), 3.91 (s, 3H); 13C NMR (100 MHz, CDCl3) d (ppm)
194.5, 158.3, 148.2, 132.7, 128.9, 128.8, 122.9, 120.8, 111.3, 55.5;
HRMS (ESI TOF) m/z calcd for C10H11O2 [M+H]+ 163.0759, found
163.0750.
2-phenylpropanal (2ab): Compound 2ab was synthesized fol-
lowing the general procedure B. Compound 2ab was obtained as
colourless oil (89%, 23.9 mg); eluent (petroleum ether/ethyl acet-
ate = 19:1); Rf = 0.5; 1H NMR (400 MHz, CDCl3)
d 9.68 (d,
J = 1.4 Hz, 1H), 7.40–7.36 (m, 2H), 7.32–7.28 (m, 1H), 7.22–7.20
(m, 2H), 3.66–3.60 (m, 1H), 1.44 (d, J = 7.1 Hz, 3H); 13C NMR
(100 MHz, CDCl3) d (ppm) 201.2, 137.8, 129.2, 128.4, 127.6, 53.1,
14.7; HRMS (ESI TOF) m/z calcd for C9H11O [M+H]+ 135.0810, found
135.0815.
Cyclohexanone (2ac): Compound 2ac was synthesized following
the general procedure B. Compound 2ac was obtained as colourless
oil (91%, 17.9 mg); eluent (petroleum ether/ethyl acetate = 99:1);
Rf = 0.6; 1H NMR (400 MHz, CDCl3): d 2.18 (dd, J = 8.4, 4.2 Hz,
4H), 1.80–1.63 (m, 4H), 1.62–1.50 (m, 2H); 13C NMR (100 MHz,
CDCl3): d 212.1, 41.8, 26.9, 24.8; HRMS (ESI TOF) m/z calcd for
C6H11O [M+H]+ 99.0810, found 99.0818.
1H-indole-3-carbaldehyde (2u): Compound 2u was synthesized
following the general procedure B. Compound 2u was obtained
as Yellow solid (91%, 26.5 mg); mp 190–195 °C; eluent (petroleum
ether/ethyl acetate = 7:3); Rf = 0.38; 1H NMR (400 MHz, CDCl3): d
10.08 (s, 1H), 8.75 (s, 1H), 8.35–8.32 (m, 1H), 7.86 (d, J = 3.1 Hz,
1H), 7.47–7.44 (m, 1H), 7.36–7.32 (m, 2H); 13C NMR (100 MHz,
DMSO-D6)
d 185.75, 139.01, 137.4, 124.39, 123.98, 122.66,
121.19, 118.49, 112.84; HRMS (ESI TOF) m/z calcd for C9H8NO [M
+H]+ 146.0606, found 146.0597.
Thiophene-3-carbaldehyde (2v): Compound 2v was synthesized
following the general procedure B. Compound 2v was obtained
as dark brown oil (89%, 20 mg); eluent (petroleum ether/ethyl
acetate = 9:1); Rf = 0.4; 1H NMR (400 MHz, CDCl3): d 9.94 (s, 1H),
8.13 (dd, J = 2.8, 1.0 Hz, 1H), 7.57–7.52 (m, 1H), 7.38 (dd, J = 5.1,
2.9 Hz, 1H); 13C NMR (100 MHz, CDCl3) d 185.1, 143.1, 136.8,
127.5, 125.5; HRMS (ESI TOF) m/z calcd for C5H4OS [M+H]+
113.0061, found 113.0070.
((2,4-dinitrophenyl)methylene)bis(p-tolylsulfane) (3): Compound
3 was synthesized following the general procedure A. Compound
3 was obtained as brown colour viscous oil (91%, 554 mg); eluent
(petroleum ether/ethyl acetate = 7:3); Rf = 0.5; 1H NMR (400 MHz,
CDCl3): d 8.60 (d, J = 2.3 Hz, 1H), 8.31 (ddd, J = 8.7, 2.4, 0.4 Hz,
1H), 8.04 (d, J = 8.7 Hz, 1H), 7.24–7.21 (m, 4H), 7.08–7.05 (m,
4H), 6.29 (s, 1H), 2.31 (s, 6H); 13C NMR (100 MHz, CDCl3): d
147.73, 146.72, 142.07, 139.62, 133.91, 132.48, 130.23, 128.52,
1-(thiophen-2-yl)ethanone (2w): Compound 2w was synthe-
sized following the general procedure B. Compound 2w was
obtained as dark yellow oil (95%, 24 mg); eluent (petroleum
ether/ethyl acetate = 9:1); Rf = 0.45; 1H NMR (400 MHz, CDCl3) d
7.7 (dd, J = 3.8, 1.2 Hz, 1H), 7.64 (dd, J = 5.0, 1.2 Hz, 1H), 7.13 (dd,
J = 5, 3.8 Hz, 1H), 2.57 (s, 3H); 13C NMR (100 MHz, CDCl3): d
190.81, 144.59, 133.86, 132.57, 128.19, 26.96; HRMS (ESI TOF) m/
z calcd for C6H7OS [M+H]+ 127.0218, found 127.0217.
Acetophenone (2x): Compound 2x was synthesized following
the general procedure B. Compound 2x was obtained as colourless
oil (94%, 23.1 mg); eluent (petroleum ether/ethyl acetate = 19:1);
Rf = 0.61; 1H NMR (400 MHz, CDCl3): d 7.97–7.94 (m, 2H), 7.58–
7.54 (m, 1H), 7.46 (t, J = 7.6 Hz, 2H), 2.59 (s, 3H); 13C NMR
(100 MHz, CDCl3): d 198.3, 137.2, 133.2, 128.7, 128.4, 26.7; HRMS
(ESI TOF) m/z calcd for C8H9O [M+H]+ 121.0653, found 121.0655.
9H-fluoren-9-one (2y): Compound 2y was synthesized following
the general procedure B. Compound 2y was obtained as yellow
solid (97%, 35 mg); mp 80–81 °C; eluent (petroleum ether/ethyl
acetate = 8:2); Rf = 0.42; 1H NMR (400 MHz, CDCl3): d 7.64–7.56
(m, 2H), 7.47–7.38 (m, 4H), 7.24 (ddt, J = 8.1, 5.5, 2.6 Hz, 2H); 13C
NMR (100 MHz, CDCl3): d 194, 144.4, 134.7, 134.1, 129.1, 124.3,
126.99, 120.05, 54.63, 21.37; HRMS (ESI TOF) m/z calcd for C21H18-
N2O4S2 [M]+ 426.0708, found 426.0698.
2,4-dinitrobenzaldehyde (3a): Compound 3a was synthesized
following the general procedure A. Compound 3a was obtained
as yellow solid (85%, 33.3 mg); mp 63–68 °C; eluent (petroleum
ether/ethyl acetate = 7:3); Rf = 0.5; 1H NMR (400 MHz, CDCl3): d
10.48 (s, 1H), 8.97 (d, J = 2.1 Hz, 1H), 8.63 (ddd, J = 8.4, 2.2,
0.7 Hz, 1H), 8.15 (d, J = 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3): d
186.5, 150.1, 149.5, 135.5, 131.6, 128.7, 120.3; HRMS (ESI TOF)
m/z calcd for C7H5N2O5 [M+H]+ 197.0198, found 197.0202.
1,2-di-p-tolyldisulfane (3b): Compound 3b was obtained as yel-
low colour oil (60%, 29.6 mg); yellow solid; eluent (petroleum
ether/ethyl acetate = 18:1); Rf = 0.5; 1H NMR (400 MHz, CDCl3): d
7.92 (d, J = 8.5 Hz, 4H), 7.41 (d, J = 8.0 Hz, 4H), 2.49 (s, 6H); 13C
NMR (100 MHz, CDCl3): d 147.0, 141.7, 130.4, 127.1, 21.9; HRMS
(ESI TOF) m/z calcd for C14H14S2 [M]+ 246.0537, found 246.0530.
Funding sources
DST-SERB (EMR/2015/000909), New Delhi, Govt. of India.
Please cite this article as: P. D. Dharpure, A. Bhowmick, P. K. Warghude et al., Visible-light mediated facile dithiane deprotection under metal free condi-