10.1002/ejoc.201700670
European Journal of Organic Chemistry
FULL PAPER
3a: 82 % yield. 1H NMR (CDCl3, 400.14 MHz): δ 4.7 (b, Sn-H), 2.4-0.3 (b,
PNB backbone), 1.5 (b, CH2, Bu), 1.3 (b, CH2, Bu), 0.9 (b, CH3, Bu). 13C
CP-MAS NMR (100.61 MHz): δ 70-40 (b, PNB backbone), 38 (b), 35 (b),
21.6 (b), 16.4 (b). 119Sn CP-MAS NMR (149.21 MHz): δ -90.5 (b). IR
(neat, cm–1), ν(Sn-H): 1803 (s). The polymer contains 2.43 mg (0.069
mmol) of Cl/g of polymer, which indicates 96 % of chloride substitution.
analyzed by 1H NMR. MeOH (10 mL) was poured and the polymer was
filtered and washed with MeOH (3 x 5 mL), Et2O (3 x 5 mL) and air-dried.
The polymer was recovered quantitatively. The MeOH solution was
evaporated and the residue was extracted with Et2O. The ethereal
solution was evaporated to dryness. The residue was subjected to
preparative TLC (silica) using hexane as eluent to separate the residual
silicon polymeric byproducts from the mixture of reaction products: 5.4
mg (mixture of isomers). The dehalogenated products were identified by
comparison to the NMR data reported in the literature.[28]
3b-ins: 97 % yield. 13C CP-MAS NMR (100.61 MHz): δ 65-35 (b, PNB
backbone), 37.9 (b), 35.1 (b), 21.7 (b), 16.1 (b). 119Sn CP-MAS NMR
(149.21 MHz): δ -85 (b). IR (neat, cm–1), ν(Sn-H): 1803 (s). The polymer
contains 3 mg (0.085 mmol) of Cl/g of polymer, which indicates 96 % of
chloride substitution.
Acknowledgements
Financial support from the Spanish MINECO (SGPI, grants
CTQ2013-48406-P and CTQ2016-80913-P) and the Junta de
Castilla y León (fellowship to RGL co-funded by the European
Social Fund) is gratefully acknowledged. We are indebted to
Prof. Josep Bonjoch (Univ. of Barcelona) for useful disscussions.
Dehalogenation reactions
General
dehalogenation
procedure
using
VA-PNB-
NB(CH2)4SnBu2Cl: In
a
Schlenk flask with a screw cap, the
corresponding RX (0.027 mmol), polymer 2b-ins (3.84 mg, 5.48 x 10-3
mmol of Sn-Cl), AIBN (0.9 mg, 5.48 x 10-3 mmol), PMHS (5 mg, 0.084
mmol Si-H) and KF (9.51 mg, 0.162 mmol) were mixed in THF (1.3 mL)
and water (0.1 mL) under a nitrogen atmosphere and stirred at 80 ºC for
4 h. After this time, the crude reaction mixture was analyzed by 1H NMR.
MeOH (10 mL) was poured and the polymer was filtered and washed
with MeOH (3 x 5 mL), Et2O (3 x 5 mL) and air-dried. The polymer was
quantitatively recovered. All the dehalogenated products in Table 3 are
commercial and were identified by comparison to the NMR data of
authentic samples.
Keywords: Radical reactions • tin • supported catalysts •
polynorbornene • dehalogenation
[1]
[2]
a) W. P. Neumann, Synthesis, 1987, 665-683. b) M. Pereyre, J. –P.
Quintard, A. Rahm, Tin in Organic Synthesis, Butterworths, London,
1987. c) Tin Chemistry: Fundamentals, Frontiers and Applications, (Eds.
A. G. Davies, M. Gielen, K. H. Pannell, R. T. Tiekink), Wiley, Chichester,
2008.
Dehalogenation procedure using VA-PNB-NB(CH2)4SnHBu2: In a
Schlenk flask with a screw cap, 9-bromophenanthrene (7.19 mg, 0.027
mmol), polymer 3b (20.25 mg, 0.040 mmol of Sn-H) and AIBN (0.9 mg,
5.48 x 10-3 mmol) were mixed in THF (1.4 mL) under a nitrogen
atmosphere and stirred at 80 ºC for 4 h. The crude reaction mixture was
analyzed by 1H NMR. MeOH (10 mL) was poured and the polymer was
filtered and washed with MeOH (3 x 10 mL), Et2O (3 x 10 mL) and air-
dried. It was quantitatively recovered.
The toxicity of organotin compounds SnR3X strongly depends on the
nature of the R group and, for alkyl derivatives, it decreases upon
increasing the length of the alkyl chain, R= Me being the most toxic. a)
Y. Arakawa, O. Wada. T. H. Yu, Toxicol. Appl. Pharmacol. 1981, 60, 1-
7. b) B. Buck, A. Mascioni, L. Que, Jr., G. Veglia, J. Am. Chem. Soc.
2003, 125, 13316-13317 and references therein. c) K. E. Apple, Drug.
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[5]
a) P. A. Baguely, J. C. Walton, Angew. Chem. Int. Ed. 1998, 37, 3072-
3082. b) A. Studer, S. Amrein, Synthesis 2002, 835-849.
Recycling procedure: In
a Schlenk flask with a screw cap, 9-
bromophenanthrene (0.2 g, 0.76 mmol), polymer 2b-ins (0.29 g, 0.38
mmol of Sn), PMHS (0.14 g, 2.29 mmol) and KF (0.0581 g, 4.57 mmol)
were mixed in THF (36 mL) and water (2.8 mL) under a nitrogen
atmosphere and stirred at room temperature for 15 min.[35] A solution of
AIBN (0.025 g, 0.15 mmol) in THF (2 mL) was added, and the mixture
was stirred at 80 ºC for 2 h. A new solution of AIBN (0.025 g, 0.15 mmol)
in THF (2 mL) was added, and the mixture was stirred at 80 ºC for 2 h.
The resulting reaction mixture was concentrated at reduced pressure to
c.a. 15 mL and MeOH (30 mL) was added. The polymer was filtered,
washed with MeOH (3 x 30 mL), Et2O (3 x 30 mL) and air-dried. It was
almost quantitatively recovered (90-100% yield) and stored to be reused
in a subsequent reaction. The MeOH solution was evaporated and the
residue was extracted with Et2O. The ethereal solution was evaporated
to dryness and was subjected to preparative TLC (silica) using hexane as
eluent. A yellowish solid was obtained, 130.9 mg, 96 % yield. The
experiments collected in Table 5 were carried out in the same way.
SnHBu3 is actually the correct IUPAC name (see IUPAC Red Book)
even though organic chemists are more used to Bu3SnH.
Borane derivatives: a) E. J. Corey, W. Suggs, J. Org. Chem. 1975, 40,
2554-2555. b) G. Stork, P. M. Sher, J. Am. Chem. Soc. 1986, 108, 303-
304. c) D. E. Bergbreiter, J. R. Blanton, J. Org. Chem. 1987, 52, 472-
473. Silanes: d) J. Lipowitz, S. A. Bowman, J. Org. Chem. 1973, 38,
162-165. e) D. S. Hays, G. C. Fu, J. Org. Chem. 1996, 61, 4-5. PMHS:
f) K. Hayashi, J. Iyoda, I. Shiihara, J. Organomet. Chem. 1967, 10, 81-
91. g) R. M. Lopez, D. S. Hays, G. C. Fu, J. Am. Chem. Soc. 1997, 119,
6949-6950. h) I. Terstiege, R. E. Maleczka, Jr. J. Org. Chem. 1999, 64,
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[6]
A discussion of these methods as well as the use of polymeric and
other tin supports can be found in several reviews: a) D. Young in Tin
Chemistry-Fundamentals, Frontiers and Applications (Eds.: A. G.
Davies, M. Gielen, K. H. Pannell, R. T. Tiekink) Wiley, Chichester, 2008,
Ch. 5, pp. 653-665. b) N. Carrera, A. C. Albéniz, Eur. J. Inorg. Chem.
2011, 2347-2360. c) E. Le Grognec, J.-M. Chretí en, F. Zammattio, J.-P.
Quintard, Chem. Rev. 2015, 115, 10207−10260.
Cyclization reaction. In a Schlenk flask with a screw cap, 1-bromo-2-
(prop-2-en-1-yloxy)naphthalene (4, 7.21 mg, 0.027 mmol), polymer 2b-
ins (3.84 mg, 5.48 x 10-3 mmol of Sn-Cl), AIBN (0.9 mg, 5.48 x 10-3
mmol), PMHS (5 mg, 0.084 mmol Si-H) and KF (9.51 mg, 0.162 mmol)
were mixed in THF (1.3 mL) and water (0.1 mL) under a nitrogen
atmosphere and stirred at 80 ºC for 4 h. The crude reaction mixture was
[7]
[8]
[9]
D. L. J. Clive, J. Wang, J. Org. Chem. 2002, 67, 1192-1198 .
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P. D. Pham, S. Legoupy, Tetrahedron Lett. 2009, 50, 3780-3782.
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