6888
S. Muthusamy, K. Selvaraj / Tetrahedron Letters 54 (2013) 6886–6888
11. General procedure: A mixture of N-substituted spiro-1,3-dithiolaneoxindole
Rh2(OAc)4
O
N2
2a–e or spiro-1,3-dithianeoxindole 2e, 2f (1 mmol) and rhodium(II) acetate
dimer (2.9 mg, 0.56 mol %) catalyst was taken in dry CH2Cl2 (20 ml) and stirred
under argon atmosphere. A solution of N-substituted 3-diazoindol-2-ones 1a–
d (1.2 mmol) in dry CH2Cl2 (10 ml) was added dropwise with the help of
syringe pump over 1 h duration and further stirred at room temperature for
the appropriate duration. The reaction was monitored using TLC. After the
completion of reaction, the solvent was removed under reduced pressure. The
residue was subjected to column chromatography (silica gel, 100–200 mesh,
EtOAc/hexane 70:30) to furnish the ring enlarged product of dispiro-dithianes
or -dithiepanes 3a–m.
Rh2(OAc)4
-N2
O
N
N
R1
R1
4
1
R2
( )n
S
S
N
12. All the new compounds exhibited spectral data consistent with their
structures. Synthesis of 1,100-dimethyldispiro[indole-3,20-[1,4]dithiane-30,300-
indole]-2,200(1H,100H)-dione (3a): A solution of 1c (178 mg, 0.75 mmol) in dry
dichloromethane (10 ml) was added dropwise to a solution containing spiro-
1,3-dithiolaneoxindole 2a (150 mg, 0.63 mmol) and rhodium(II) acetate dimer
(2.9 mg, 0.56 mol %) in dry dichloromethane (20 ml) and then followed as
described in general procedure to afford product 3a in 81% yield as a colourless
solid; mp 264–266 °C; mmax (neat) 2921, 2851, 1699, 1606, 1489, 1372, 1342,
O
R3
2
( )n
R2
S
S
( )n
S
R2
S
1255, 1088, 922, 752 cmꢀ1 1H NMR (CDCl3, 400 MHz) d = 2.74–2.84 (m, 2H,
;
O
SCH2), 3.16 (s, 6H, NCH3), 4.27–4.37 (m, 2H, SCH2), 6.55 (d, 2H, J = 7.6 Hz, ArH),
6.86 (td, 2H, J1 = 7.6 Hz, J2 = 0.8 Hz, ArH), 7.11 (td, 2H, J1 = 7.6 Hz, J2 = 1.2 Hz,
ArH), 7.18 (dd, 2H, J1 = 7.2 Hz, J2 = 0.4 Hz, ArH); 13C NMR (CDCl3, 100 MHz) d
25.50 (SCH2), 25.97 (NCH3), 45.90 (quat-C), 107.89 (@CH), 122.37 (@CH),
126.24 (quat-C), 129.74 (@CH), 142.88 (quat-C), 173.49 (C@O). HRMS (ESI)
O
O
O
N
N
N
N
R3
R1
R3
R1
3
5
calcd for
C
20H18N2O2S2 (M+1)+: 383.0888 found 383.0883. Synthesis of 1-
methyl-100-benzyldispiro[indole-3,20-[1,4]dithiane-30,300-indole]-2,200(1H,100H)-
Scheme 2. Plausible mechanism.
dione (3c): A solution of 1a (104 mg, 0.44 mmol) in dry dichloromethane
(10 ml) was added dropwise to
a
solution containing spiro-1,3-
dithiolaneoxindole 2a (100 mg, 0.40 mmol) and rhodium(II) acetate dimer
(2.9 mg, 0.56 mol %) in dry dichloromethane (20 ml) and then followed as
described in general procedure to afford product 3c in 60% yield as a colourless
solid; mp 184–186 °C; mmax (neat) 2921, 2851, 1698, 1606, 1489, 1469, 1372,
Acknowledgments
1342, 1256, 1088, 752 cmꢀ1 1H NMR (CDCl3, 400 MHz) d = 2.80–2.83 (m, 2H,
;
This research was supported by the Department of Science and
Technology (DST), New Delhi. K.S. thanks UGC-RFMS for a fellow-
ship. We thank DST, New Delhi, for providing 400 MHz NMR facil-
ity under FIST program.
SCH2), 3.19 (s, 3H, NCH3), 4.31–4.34 (m, 2H, SCH2), 4.91 (q, 2H, J = 15.6 Hz,
NCH2), 6.50 (d, 1H, J = 8 Hz, ArH), 6.56 (d, 1H, J = 8 Hz, ArH), 6.68 (td, 1H,
J1 = 7.6 Hz, J2 = 0.9 Hz, ArH), 6.84 (td, 1H, J1 = 7.6 Hz, J2 = 0.9 Hz, ArH), 7.03 (td,
1H, J1 = 7.7 Hz, J2 = 1.2 Hz, ArH), 7.08–7.13 (m, 2H, ArH), 7.20 (dd, 1H,
J1 = 7.6 Hz, J2 = 0.8 Hz, ArH), 7.23–7.29 (m, 5H, ArH); 13C NMR (CDCl3,
100 MHz) d 25.62 (SCH2), 25.68 (SCH2), 26.05 (NCH3), 43.69 (NCH2), 45.66
(quat-C), 45.88 (quat-C), 107.90 (@CH), 109.03 (@CH), 122.49 (@CH), 122.58
(@CH), 124.61 (@CH), 125.10 (@CH), 126.28 (quat-C), 126.35 (quat-C), 127.56
(@CH), 127.66 (@CH), 128.74 (@CH), 129.68 (@CH), 129.70 (@CH), 135.35
(quat-C), 142.20 (quat-C), 142.81 (quat-C), 173.39 (C@O), 173.52 (C@O); HRMS
(ESI) calcd for C26H22N2O2S2 (M+1)+: 459.1201 found 459.1208. Synthesis of 1-
benzyl-100-methyldispiro[indole-3,20-[1,4]dithiepane-30,300-indole]-2,200(1H,100H)-
dione (3k): A solution of 1a (123 mg, 0.49 mmol) in dry dichloromethane
Supplementary data
Supplementary data associated with this article can be found, in
(10 ml) was added dropwise to
a
solution containing spiro-1,3-
References and notes
dithianeoxindole 2f (100 mg, 0.41 mmol) and rhodium(II) acetate dimer
(2.9 mg, 0.56 mol %) in dry dichloromethane (20 ml) and then followed as
described in general procedure to afford product 3k in 67% yield as a colourless
solid; mp 189–191 °C; mmax (neat) 2924, 2852, 1698, 1609, 1489, 1472, 1372,
1341, 1256, 1088, 750 cmꢀ1 1H NMR (CDCl3, 400 MHz) d = 2.17–2.32 (m, 2H,
;
SCH2), 2.51–2.58 (m, 2H, CCH2), 3.11 (s, 3H, NCH3), 4.79–4.92 (m, 4H, CH2),
6.42 (d, 1H, J = 7.6 Hz, ArH), 6.52 (d, 1H, J = 8.0 Hz, ArH), 6.65 (td, 1H,
J1 = 8.0 Hz, J2 = 1.2 Hz, ArH), 6.79 (td, 1H, J1 = 7.6 Hz, J2 = 0.8 Hz, ArH), 6.95
(td, 1H, J1 = 7.6 Hz, J2 = 0.8 Hz, ArH), 7.04 (td, 1H, J1 = 7.6 Hz, J2 = 0.8 Hz, ArH),
7.08–7.10 (m, 2H, ArH), 7.17–7.19 (m, 4H, ArH), 7.26 (dd, 1H, J1 = 7.6 Hz,
J2 = 0.4 Hz, ArH); 13C NMR (CDCl3, 100 MHz) d 25.82 (SCH2), 26.00 (SCH2), 26.05
(NCH3), 31.42 (CCH2) 43.58 (NCH2), 52.70 (quat-C), 53.25 (quat-C), 108.03
(@CH), 109.14 (@CH), 122.60 (@CH), 122.75 (@CH), 125.10 (@CH), 125.65
(@CH), 126.10 (quat-C),127.34 (@CH), 127.55 (@CH), 128.69 (@CH), 129.28
(@CH), 135.30 (quat-C), 141.35 (quat-C), 141.92 (quat-C), 172.21 (C@O), 172.43
(C@O); HRMS (ESI) calcd for C27H24N2O2S2 (M+1)+: 473.1357 found 473.1355.
Crystal data for the compound 3c: (CCDC 959983) C20H18N2O2S2, M = 382.48,
0.34 ꢁ 0.25 ꢁ 0.14 mm, Monoclinic, space group p-21 with a = 12.5972(12) Å,
b = 14.9269(14) Å, c = 9.4547(9) Å,
a
= 90.00, b = 91.077(2),
c = 90.00,
V = 1777.5(3) Å3, T = 293(2) K, R1 = 0.0351, wR2 = 0.0958 on observed data,
z = 4, Dcalcd = 1.429 mg cm–3, F(000) = 800, Absorption coefficient = 0.317 mm–
1, k = 0.71073 Å, 4028 reflections were collected on a smart apex CCD single
crystal diffractometer 3595 observed reflections (I P 2
r (I)). The largest
difference peak and hole = 0.257 and ꢀ0.214 eÅ–3, respectively. The structure
was solved by direct methods and refined by full-matrix least squares on F2
using SHELXL-97 software.
13. See Refs. 3 and 4.