recovered. 503.6 g of DEC and 2.27 gm catalyst were retained;
adding 78.0 gm of DEC and 80.0 gm of GL, the catalyst mixture
was recycled. Recovered hexane was reused for the next cycle.
The same procedure was followed for other catalysts.
EG and PG was used in a similar manner and purification
was carried out by distillation.
benzthiazole (436 mg, 2.9 mmol) in 25 mL acetone were
stirred for 3 h while a white precipitate appeared during the
reaction. The solution was filtered to remove any insolubles and
evaporated to dryness◦to yield a solid white product. Yield 25%;
Mp, 198 ◦C (lit.16 195 C). Elemental analysis: C, 45.67; H, 3.37;
Cl, 11.24; Sn, 37.50. Calculated for C48H40Sn4O2Cl2. C,45.56; H,
3.19; Cl,11.21; Sn, 37.52. ESI-TOF mass: m/z ¥ 2, 1265.441,
1
Preparation of catalysts
(calculated 1265.42). H NMR: dH(300 MHz; CDCl3; Me4Si);
7.61 (8H, m, oPh), 8.58 (12H, m, m,pPh).
Preparation of 1,3-dichloride-1,1–3,3-tetrabutyldistannoxane
(1a). 1a was synthesized according to published procedures.25
A mixture of Bu2SnO (1.0 g, 4.0 mmol) and Bu2SnCl2 (1.22 g,
4.0 mmol) in toluene (50 mL) was refluxed for several hours.
After 10 h reflux, the reaction mixture became a clear solu-
tion. The reaction was further refluxed for another 7 h. The
hot mixture was filtered and concentrated in vacuum to get
1,3-dichlorotetra-n-butyldistannoxane (1a). Pure product was
obtained by recrystallizing from tolue◦ne. Yield 95%; Melting
point, 110 ◦C (from ethanol) (lit.25 110 C). Elemental analysis:
Found C, 34.61; H, 6.52; Cl, 12.85; Sn, 43.01. Calculated for
C32H72Sn4O2Cl2: C, 34.64; H, 6.54; Cl, 12.83; Sn, 42.95. ESI-TOF
mass: m/z 1106.47. 1H NMR: dH(300 MHz; CDCl3; Me4Si) 0.87
(12H, t, Me), 1.4 (8H, m, Sn–CH2–), 1.8 (16H, m, CH2–CH2).
1b and 1c. These catalysts were synthesized following a
previously published literature method.26
Estimation of Cl- and Sn in the catalysts
A representative method for the estimation of % of Cl- and
Sn of catalyst 1a is described here. This was run similarly
wherever required in order to obtain the % of Cl- and Sn: 1a
(110 mg, 0.1 mmol) was digested with an equivalent amount of
concentrated HNO3 (69%) in a porcelain crucible for 5 h. The
resultant digested mass was then evaporated to dryness. The
solid obtained after evaporation was dissolved in 10 mL water
and acidified with dilute HNO3 (6.9%) until the solution turned
clear. After filtering the solution, the filtrate was transferred into
a 100 mL volumetric flask and diluted with water. The solution
was then analyzed to estimate Cl- by using a Metrohm column
in an ion chromatography method. The same solution was used
to determine Sn content by ICP-OES.
Preparation of 1,3-dichloride-1,1-dibutyl-3,3-diphenyldistan-
noxane (1b). Bu2SnO (0.720 g, 2.90 mmol) and Ph2SnCl2 (1.0 g,
2.908 mmol) were dissolved in 25 mL acetone in a 100 mL round
bottom flask and refluxed for 3 h while stirring the reaction
mixture. Most of the solid dissolved within 3 h of the reaction.
After filtration, the reaction mixture was cooled at room
temperature and concentrated to obtain a solid product. Pure
needle shaped crystals of 1b were obtained after crystallizing the
solid from hexane. Yield 90%; Mp, 148 ◦C. Elemental analysis:
Found C, 40.58; H, 4.54; Cl, 12.03, Sn, 40.06. Calculated for
C40H56Sn4O2Cl2: C, 40.52; H, 4.76; Cl, 11.96; Sn, 40.05. ESI-
Acknowledgements
We greatly acknowledge financial help from Reliance Industries
Limited. We are very much thankful to Dr. A. J. Sophia, Dr.
G. Kalpana, G. M. Desai and K. Solanki for analytical help.
References
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◦
mixture under vacuum (55 C, 65 mmHg). Pure crystalline 1c
was obtained after crystallizing the solid from hexane. Yield
◦
75%; Mp 152 C (lit.26 149 ◦C). Elemental analysis: C, 40.54;
H, 4.28; Cl, 12.01; Sn, 40.03. Calculated for C40H56Sn4O2Cl2.
C,40.52; H, 4.76; Cl,11.96; Sn, 40.05. ESI-TOF mass: m/z ¥ 2,
1185.813, (Calculated 1185.46). 1H NMR: dH(300 MHz; CDCl3;
Me4Si); 1.22 (6H, t, CH3), 1.91 (4H, m, Sn–CH2–), 2.77 (8H, m,
–CH2–CH2–), 7.41 (6H, m,oPh), 8.18 (6H, m, m,pPh).
Preparation of 1,3-dichloride-1,1,3,3-tetraphenyldistannoxane
(1d). 1d was synthesized as per the literature reported
procedure.27 Ph2SnCl2 (1.0 g, 2.9 mmol) and 2-amino-
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