A. Maia et al. / Tetrahedron 60 (2004) 10111–10115
10115
4.2. Materials and solvents
progress was monitored by GLC analysis of the organic
phase, with respect to an internal standard. Dodecane was
used in all reactions except for the reduction of benz-
aldehyde, where anisole was employed. In all cases the mass
balance was $95%.
Silicon polypodands 1–7 were prepared following a
previously reported procedure.10 Their structures were
proved by 1H, 13C and 29Si NMR spectroscopy.10
Polypodand, yield (%), boiling point (8C)/mm Hg are as
follows: 1, 56, 254–256/1.1; 2, 51, 258–260/1.1; 3, 60,
255–258/0.2; 4, 55, 254–255/1.1; 5, 75, 113–115/10; 6, 78,
249–252/1.1; 7, 79, 243–247/1.1.
4.5. General procedure for the epoxide opening reaction
(4)
Solid LiI (10 mol/mol of catalyst) was added to a
chlorobenzene solution of catalyst (0.003 M) and the
heterogeneous mixture stirred for about 2 h. An aliquot
(3–5 ml) of the organic phase was withdrawn and the
complex titrated with 0.01 M AgNO3. The remaining
solution was added with p-toluenesulfonamide 20
(0.5 mmol) and 5 ml of a chlorobenzene solution of epoxide
(0.06 M). The reaction progress was monitored by TLC
(eluant PE/Et2O 7/3).
Ligands DCH18C6 (mixture of isomers) 11, PEG 9,
PEG400Me2 10 and TRIDENT 8 were utilized as
purchased. Octylbromide (13), benzaldeyde (14), p-toluene-
sulfonamide (20), dodecane and anisole were commercial
products, utilized as purchased. Alkali metal halides (NaI,
KI, NaBr, LiI), NaBH4, NaIO3 and C6H4(CO)2NK (16),
were AnalaR grade commercial products, kept in a
dessiccator under vacuum.
Dry (Fluka) chlorobenzene and acetonitrile (H2O #20 ppm)
were used. 1,2-Phenylglycidol 18 was a commercial
product, purified by distillation and kept over molecular
sieves.
Acknowledgements
The present work was performed in the framework of a
NATO Science Fellowship (37/J/2000) granted to B.L. and
grant KBN No. T09A 096 20. Financial support of CNR
`
and Ministero dell’Universita e della Ricerca Scientifica e
Tecnologica (MURST) is also acknowledged.
Octyl methanesulfonate 12, bp 92–94 8C at 0.003 mm Hg,
n2D0 1.4392, was prepared according to the literature
(bp 98 8C at 1.5 mm Hg, n2D0 1.4390).13
4.3. Extent of complexation
The extent of complexation of polypodands 1–7 and
polyethers 8–11 under SL-PTC conditions was determined
by stirring a standardized chlorobenzene (or acetonitrile)
solution (10–20 ml) of ligand (0.02–0.05 M) with 10–
50 molar equiv of salt MY, as a solid phase, in a flask
thermostatted at 60, 80 8C. The system was stirred for
4–12 h, then kept without stirring for an additional 10 min
to allow good separation of the two phases. Aliquots
(5–8 ml) of the organic phase were centrifuged, samples
(2–3 ml) were withdrawn and titrated with 0.01 M AgNO3
or 0.01 M HCl (potentiometric titration). In the complexa-
tion of NaBH4 a chlorobenzene solution of ligand (0.01 M)
was stirred for 10–12 h with 30 molar equiv of NaBH4 as a
solid phase in a flask thermostatted at 25 8C. Aliquots
(3–5 ml) of the organic phase were centrifuged and samples
(2–3 ml) were withdrawn and added to an aqueous solution
of NaIO3 (1.2 mol/mol of BH24 ).14
References and notes
1. Kron, T. E.; Tsvetkov, E. N. Russ. Chem. Rev. 1990, 59,
283–298, and references cited therein.
2. Gokel, G. W.; Murillo, O. Podands. Comprehensive Supra-
molecular Chemistry—Molecular Recognition: Receptors
for Cationic Guests; Gokel, G. W., Ed.; Elsevier: Oxford,
UK, 1996; Vol. 1, pp 1–33.
3. Landini, D.; Maia, A.; Penso, M. Anion Activation. Compre-
hensive Supramolecular Chemistry—Molecular Recognition:
Receptors for Cationic Guests; Gokel, G. W., Ed.; Elsevier:
Oxford, UK, 1996; Vol. 1, pp 417–464.
4. Pedersen, C. J.; Frensdorff, H. K. Angew. Chem., Int. Ed. Engl.
1972, 11, 16–25, and references cited therein.
5. Lehn, J. M. Angew. Chem., Int. Ed. Engl. 1988, 27, 89–112.
6. Gobbi, A.; Landini, D.; Maia, A.; Delogu, G.; Podda, G. J. Org.
Chem. 1994, 59, 5059–5062.
After magnetic stirring for about 20 m the iodide formed by
the reaction:
7. Landini, D.; Maia, A.; Podda, G. Gazz. Chim. Ital. 1995, 125,
583–585.
8. Maia, A. Pure Appl. Chem. 1995, 67, 697–702.
9. Maia, A.; Landini, D.; Leska, B.; Schroeder, G. Tetrahedron
Lett. 2003, 44, 4149–4151.
3BH24 þ 4IO32 ! 4I2 þ 3H2BO32 þ 3H2O
was potentiometrically titrated with 0.01 M AgNO3.14
10. Leska, B.; Gierczyk, B.; Eitner, K.; Rybachenko, V. I.;
Schroeder, G. Supramol. Chem. 2004, 16(5), 303–310.
11. Gobbi, A.; Landini, D.; Maia, A.; Secci, D. J. Org. Chem.
1995, 60, 5954–5957.
4.4. General procedure for the reactions (1–3) under
SL-PTC conditions
Solid salt MY (2.5–12.5 mmol) was added to a chloro-
benzene or acetonitrile solution (5 ml) of substrate (1–
2.5 mmol), catalyst (0.1–0.25 mmol) and an internal
standard (0.5–1.25 mmol). The heterogeneous mixture
was heated at the appropriate temperature (see Tables
1–3) under vigorous magnetic stirring. The reaction
12. Landini, D.; Maia, A.; Pinna, C. Arkivoc 2004(iii),
202–212.
13. Williams, H. R.; Mosher, H. S. J. Am. Chem. Soc. 1954, 76,
2984–2987.
14. Lyttle, D. A.; Jensen, E. H.; Struck, W. A. Anal. Chem. 1952,
24, 1883–1884.