Synthesis, stereoselective reactions, and reactivity of 9-triptycyldimethyltin hydride

Article abstract of DOI:10.1021/om049104z

The synthesis of the new compounds 9-triptycyldimethyltin bromide (2) and 9-triptycyldimethyltin hydride (3) and some of their physical properties are described. The radical addition of 3 to methyl (E)-2,3-diphenylpropenoate gave the threo adducts as the

Full text of DOI:10.1021/om049104z

1992
Organometallics 2005, 24, 1992-1995
Synthesis, Stereoselective Reactions, and Reactivity of
9-Triptycyldimethyltin Hydride
Vero´nica I. Dodero,† M. Bele´n Faraoni,† Dar´ıo C. Gerbino,†,‡ Liliana C. Koll,†,§
Adriana E. Zu´n˜iga,† Terence N. Mitchell,*,| and Julio C. Podesta´*,†,§
Instituto de Investigaciones en Quı´mica Orga´nica, Departamento de Quı´mica,
Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahı´a Blanca, Argentina, CONICET,
Buenos Aires, Argentina, CIC, Provincia de Buenos Aires, Buenos Aires, Argentina,
and Fachbereich Chemie der Universita¨t Dortmund, D-44221 Dortmund, Germany
Received November 18, 2004
Scheme 1. Synthesis of 9-Triptycyldimethyltin
Hydride (3)
Summary: The synthesis of the new compounds 9-trip-
tycyldimethyltin bromide (2) and 9-triptycyldimethyltin
hydride (3) and some of their physical properties are
described. The radical addition of 3 to methyl (E)-2,3-
diphenylpropenoate gave the threo adducts as the only
products. The results obtained in the addition of hydride
3 to mono- and disubstituted alkynes under radical and
palladium-catalyzed conditions indicate that these reac-
tions take place with high stereoselectivity. The chemical
reactivity of these vinylstannanes is similar to that of
vinyltriorganostannanes containing smaller organic
ligands. Full 1H, 13C, and 119Sn NMR characteristics are
included.
Introduction
In previous studies we have shown that in triorga-
notin hydrides the size of the organic ligands attached
to the tin atom affects not only the reactivity but
also the stereoselectivity of the reactions of these
hydrides.1 We have also shown that the vinylstannanes
obtained via hydrostannation with tin hydrides contain-
ing bulky substituents such as neophyl groups are more
stable than their analogues containing less voluminous
ligands: such as, for example, n-butyl.2 Following our
studies on the synthesis of organotin hydrides contain-
ing bulky organic ligands and on the effect of the volume
of the substituents on the stereochemistry of hydrostan-
nations, we now wish to report the synthesis of 9-trip-
tycyldimethyltin hydride (3) and the results obtained
in the hydrostannation of some substituted alkenes and
alkynes using this hydride.
our starting material. In the literature there are some
references to the synthesis of 1,3,4 as well as of some
related 9-triptycyltin derivatives.5 We repeated these
synthetic routes many times, starting from 9-bromoan-
thracene, always obtaining 1 in very low total yields (8-
20%). We were able to improve the yields only up to 25%
using a combination of the methods detailed in refs 3
and 4 (see Experimental Section). With 1 as the starting
material, 9-triptycyldimethyltin hydride (3) was ob-
tained according to Scheme 1.
Results and Discussion
To obtain 9-triptycyldimethyltin hydride (3), we con-
sider it convenient to use 9-triptycyltrimethyltin (1) as
As shown in Scheme 1, whereas the conversion of 1
into the corresponding bromide 2 is achieved in 91%
yield only after 3 days at 50 °C, all attempts made to
obtain the corresponding halides by exchange reactions
between 1 and both trimethyltin chloride and dimeth-
yltin dibromide failed. These results confirm the low
reactivity of the Sn-Me bond when the trimethyltin
moiety is attached to the 9-position of tryptycene, as
reported by other authors.3 Reduction of 2 with lithium
* To whom correspondence should be addressed at the Universidad
Nacional del Sur. E-mail: jpodesta@uns.edu.ar.
† Universidad Nacional del Sur.
‡ CIC, Provincia de Buenos Aires.
§ CONICET.
| Universita¨t Dortmund.
(1) (a) Podesta´, J. C.; Giagante, N. N.; Zu´n˜iga, A. E.; Danelon, G.
O.; Mascaretti, O. A. J. Org. Chem. 1995, 59, 3747. (b) Podesta´, J. C.;
Chopa, A. B.; Radivoy, G. E.; Vitale, C. A. J. Organomet. Chem. 1995,
494, 11. (c) Vitale, C. A.; Podesta´, J. C. J. Chem. Soc., Perkin Trans. 1
1996, 2407. (d) Vitale, C. A.; Podesta´, J. C. An. Asoc. Quim. Argent.
1997, 85, 65. (e) Mandolesi, S. D.; Koll, L. C.; Podesta´, J. C. J.
Organomet. Chem. 1999, 587, 74. (f) Dodero, V. I.; Koll, L. C.;
Mandolesi, S. D.; Podesta´, J. C. J. Organomet. Chem. 2002, 650, 173.
(g) Dodero, V. I.; Mitchell, T. N.; Podesta´, J. C. Organometallics 2003,
22, 856.
(3) Ranson, R. J.; Roberts, R. M. G. J. Organomet. Chem. 1976, 107,
295.
(4) Adcock, W.; Iyer, V. S. Magn. Reson. Chem. 1991, 29, 381.
(5) Frampton, Ch. S.; Roberts, R. M. G.; Silver, J.; Warmsley, J. F.;
Yavari, B. J. Chem. Soc., Dalton Trans. 1985, 169.
(2) Dodero, V. I.; Koll, L. C.; Faraoni, M. B.; Mitchell, T. N.; Podesta´,
J. C. J. Org. Chem. 2003, 68, 10087.
10.1021/om049104z CCC: $30.25 © 2005 American Chemical Society
Publication on Web 03/15/2005

Notes
Organometallics, Vol. 24, No. 8, 2005 1993
Scheme 2. Addition of 9-Triptycyldimethyltin Hydride (3) to Methyl (E)-2,3-Diphenylpropenoate
Table 1. Triptycyldimethyltin Hydride (3) Radical
aluminum hydride in diethyl ether/THF led to the solid
9-triptycyldimethyltin hydride (3), mp 218-220 °C, in
87% yield.
Additions to Substituted Alkynesa
To determine the stereoselectivities that can be
obtained using hydride 3 in the hydrostannation of
unsaturated systems, we carried out the addition of this
hydride to methyl (E)-2,3-diphenylpropenoate (4) (Scheme
2) as well as to some terminal and internal alkynes
(Tables 1 and 2). The hydrostannation of olefin 4 was
carried out under free radical conditions: argon atmo-
sphere, in toluene at 90 °C, using an olefin to 3 ratio of
1:1, and in the presence of azobis(isobutyronitrile)
(AIBN), as shown in Scheme 2.
time temp
compd (h) (°C)
(Z)-â (Z)-R yieldb
(%) (%) (%)
119Snc
(ppm)
The 119Sn NMR spectrum of the crude product ob-
tained in the addition of hydride 3 to the olefin 4 under
free radical conditions showed only one peak at -17.1
ppm, thus indicating the formation of just one of the
two possible pairs of diastereoisomers. The 13C NMR
chemical shifts (see Experimental Section) correspond-
ing to adduct 5 could easily be assigned through the
analysis of the multiplicity of the signals by means of
DEPT experiments and taking into account the mag-
R1
R2
6
7, 8
1
1
60
60
H
H
Ph
100
70 -76.9
COOMe 91 (7) 9 (8)d,e 90 -75.1 (7),
-59.5 (8)
9
10
11
2
3
2
60 COOMe COOMe 100 f
60 Ph
60 Ph
89 -58.4
73 -66.9
67 -64.8
Ph
COOMe 100
100 f
a Conditions: reactions carried out under an argon atmosphere;
hydride to alkyne ratio 1:1; AIBN 0.01 equiv; without solvent.
b Yields of products isolated from chromatography. c In CDCl3; in
ppm with respect to Me4Sn. d From the 1H and 119Sn NMR spectra.
e In this case isomer R. f In these cases (Z)-â ) (Z)-R.
n
nitude of the J(13C,119Sn) coupling constants. The use
of the Karplus-type relationship existing6 between the
3
value of the J(13C,119Sn) coupling constants and the
dihedral angle, together with 1H NMR data, enabled us
to deduce the stereochemistry of this adduct. Thus, the
8.2 Hz value found for the 3J(Sn,CdO) coupling constant
of compound 5 (see Experimental Section) corresponds
to a dihedral angle close to 60°.6b Similarly, the 42.6
Hz value of the 3J(Sn-C-C-Ph) coupling constant for
compound 5 indicates a dihedral angle of about 180°
between the triptycyldimethyltin moiety and the phenyl
group attached to C-2.
is in agreement with what was expected when taking
into account the nature of the substituents attached to
C-2 of the starting olefin, as demonstrated in previous
studies (see Scheme 2).1e The complete diastereoselec-
tivity observed suggests that the steric volume of the
triptycyldimethyltin group has a greater effect on the
stereochemistry than that of other triorganotin moieties
used in similar studies carried out previously.1
We then studied the hydrostannation of various
terminal and internal alkynes with triptycyldimethyltin
hydride (3). We first carried out the addition of hydride
3 under the free radical conditions of argon atmosphere,
AIBN, without solvent, and 60 °C to phenyl- and
diphenylethyne, methyl propiolate, methyl 3-phenyl-
propiolate, and dimethyl acetylenedicarboxylate. The
results obtained are summarized in Table 1.
1
The H NMR spectrum of compound 5 (see Experi-
mental Section) shows 3J(H,H) coupling constants of 9.3
Hz for the protons attached to C-2 and C-3, indicating
3
that these protons are antiperiplanar. The J(Sn-C-
C-H) coupling constant, with a value of 59.9 Hz,
suggests a dihedral angle of approximately 60° between
the proton attached to C-2 and the triptycyldimethyltin
group.
This table shows that the addition of triptycyldim-
ethyltin hydride (3) leads in all cases exclusively to the
(Z)-vinylstannanes resulting from an anti attack, this
demonstrating the high stereoselectivity that can be
achieved using hydride 3. The Z geometry of compounds
6-11 was assigned by taking into account that the large
3J(Sn,H) coupling constants observed (Supporting In-
formation), all of them over 100 Hz, indicate the
existence of trans H-C-C-Sn linkages in these vinyl-
From the previous discussion, it is possible to at-
tribute a threo configuration, i.e., methyl (2R,3R)- and
(2S,3S)-2,3-diphenyl-3-triptycyldimethylstannylpropa-
noates, to the mixture of enantiomeric stereoisomers (5).
The stereochemistry of this product, obtained from the
free radical hydrostannation of olefin 4 with hydride 3,
(6) (a) Doddrell, D.; Burfitt, I.; Kitching, W.; Lee, C.-H.; Mynott, R.
J.; Considine, J. L.; Kuivila, H. G.; Sarma, R. H. J. Am. Chem. Soc.
2003, 68, 10087. (b) Mitchell, T. N.; Podesta´, J. C.; Ayala, A.; Chopa,
A. B. Magn. Reson. Chem. 1988, 26, 497.
1
stannanes. Other H and 13C NMR data (Supporting
Information) also confirmed the assigned structures.

1994 Organometallics, Vol. 24, No. 8, 2005
Notes
Table 2. Triptycyldimethyltin Hydride (3)
Palladium-Catalyzed Additions to Substituted
Alkynesa
Scheme 3. Reaction of Vinylstannanes with
Bromobencene and Iodine
time temp
compd (h) (°C)
(E)-â
(%)
(Z)-â yieldb
R (%) (%) (%)
119Snc
(ppm)
R
12, 13
8, 7
2
2
2
25 Ph
25 COOMe
70 (12) 30 (13)
85d -57.4 (12),
-57.6 (13)
89 (8) 11 (7) 90 -59.5 (8),
-75.1 (7)
14, 15
25 CH2OH 67 (14) 33 (15)
80 -60.4 (14),
-62.9 (15)
the study of the composition of the mixture of products
resulting from the reaction of organotin hydrides with
6-bromo-1-hexene under radical conditions, which will
be reported in a publication soon. The current study has
demonstrated that a tin hydide with bulky organic
ligands such as trineophyltin hydride can effect hydro-
gen transfer to the intermediate alkyl radicals more
quickly than does triptycyldimethyltin hydride (3),
showing the great effect upon the reactivity obtained
by, for example, replacing one small organic ligand such
as the methyl group of the trimethyltin hydride by the
bulkier triptycyl ligand.
a Conditions: reactions carried out under an argon atmosphere;
hydride to alkyne ratio 1:1; (PPh3)2PdCl2 2% in THF. b Yields of
products isolated from chromatography, except when otherwise
stated. c In CDCl3; in ppm with respect to Me4Sn. d Could not be
separated by chromatography; ratio obtained from the 1H and
119Sn NMR spectra.
These results are in agreement with those reported
previously for the addition of trineophyltin hydride to
the same alkynes.1f
It should be mentioned that all the attempts we made
to add hydride 3 to propargyl alcohol under radical
conditions were unsuccessful.
Experimental Section
On the other hand, the addition of 3 catalyzed by bis-
(triphenylphosphine)palladium(II) chloride to phenyl-
ethyne, methyl propiolate, and propargyl alcohol also
takes place stereoselectively, leading in most cases to
the products of a syn attack, mainly as a mixture of the
two possible regioisomers in very good yields (Table 2).
The stereochemistry of adducts 12-15 was assigned by
taking into account that the observed 3J(Sn,H) coupling
constants were in the range of 70-76 Hz, clearly
indicating a cis arrangement of the proton attached to
vinyl carbon 2 and the triptycyldimethyltin moiety
attached to vinyl carbon 1 in these vinylstannanes.
NMR spectra were obtained using a Bruker ARX 300
instrument. Mass spectra were obtained using a Finnigan
MAT Model 8230 instrument at Dortmund University (Ger-
many). Elemental analyses (C, H) were carried out with a
Carlo Erba Instrument at Santiago de Compostela University
(Spain). The melting points were determined with a Kofler hot
stage apparatus and are uncorrected. All the solvents and
reagents used were of analytical reagent grade. Dimethyl
acetylenedicarboxylate and methyl 3-phenylpropiolate were
obtained by following known techniques.9-11 9-Bromotriptycene
was obtained in 45% yield according to known procedures.12
Synthesis of 9-Triptycyltrimethyltin (1). n-Butyllithium
(38.0 mL, 1.36 M, 54 mmol in hexane) was added dropwise to
a fine suspension of 9-bromotriptycene (8.80 g, 26.3 mmol) in
dry diethyl ether (150 mL) with vigorous stirring in an argon
atmosphere. The mixture was stirred for 3 h. Then, a solution
of trimethyltin chloride (5.20 g, 26 mmol) in dry diethyl ether
(100 mL) was added. The mixture was heated under reflux
for 2 h and then left overnight at room temperature with
stirring. Distilled water (75 mL) was added cautiously, fol-
lowed by benzene (400 mL). The mixture was filtered to remove
some insoluble material and the organic phase of the filtrate
separated, washed with water, and dried over magnesium
sulfate to give a white solid. This was recrystallized twice from
cyclohexane to give 1: mp 294-295 °C (lit.3 idem); yield 6.13
g (14.72 mmol, 56%).
1
Other H and 13C NMR data confirmed the assigned
structures.
It should be noted that in this case the addition of 3
to methyl propenoate leads to a mixture of the same
products obtained in the hydrostannation under radical
conditions (see Table 1, compounds 7 and 8), but now
in a completely opposite ratio: 89% of 8 and 11% of 7
(Table 2). Another unusual feature of this reaction was
the formation of 7: i.e., the product corresponding to
an anti addition under palladium-catalyzed conditions.1f
We found that the chemical reactivity of the new
vinylstannanes is similar to that of other vinyltriorga-
nostannanes. Thus, as shown in Scheme 3, the Stille
reaction of methyl 2-triptycyldimethylstannylprope-
noate (8) with bromobenzene gives methyl 2-phenylpro-
penoate (16) in 65% yield7,8 and the iododestannylation
of (Z)-1-triptycyldimethylstannyl-1,2-diphenylethene (10)
leads quantitatively to the corresponding (Z)-1-iodo-1,2-
diphenylethene (17).
Synthesis of 9-Triptycyldimethyltin Bromide (2). To
a solution of 9-triptycyltrimethyltin (1; 1.00 g, 2.40 mmol) in
chloroform (5 mL) under argon, at room temperature, was
added dropwise with stirring a solution of bromine (0.38 g,
2.40 mmol) in chloroform (5 mL). The mixture was stirred for
1
3 days at 40-50 °C and monitored by H NMR until disap-
To estimate the relative reactivity of organotin hy-
drides, we are at present using a method based upon
(9) Ramaiah, M. Tetrahedron 1987, 43, 3641.
(10) (a) Griller, D.; Ingold, K. U. Acc. Chem. Res. 1980, 13, 317. (b)
Giese, B. Angew. Chem., Int. Ed. Engl. 1985, 24, 553.
(11) Huntress, E. H.; Lesslie, T. E.; Bornstein, J. Org. Synth.
1952,32, 55.
(12) Vogel’s Textbook of Practical Organic Chemistry, 4th ed.;
Longman: London, 1978; p 609.
(7) Scrivanti, A.; Menchi, G.; Matteoli, U. J. Mol. Catal. A: Chem.
1995, 96, 223.
(8) Hageman, H. J. Eur. Polym. J. 1999, 35, 991

Notes
Organometallics, Vol. 24, No. 8, 2005 1995
pearance of compound 1. The solvent was removed under
reduced pressure, and the crude product was recrystallized
in cyclohexane at 40 °C (the compound is sensitive to temper-
ature), affording a white crystalline solid: mp 279-281 °C;
yield 1.05 g (2.18 mmol, 91%). 1H NMR (CDCl3): δ 1.17 (s,
6 and adducts 7-11 are included in the Supporting Informa-
tion.
Addition of 9-Triptycyldimethyltin Hydride (3) to
Substituted Alkynes Catalyzed by Bis(triphenylphos-
phine)palladium(II) Chloride. Typical Procedure. To a
solution of propargyl alcohol (0.047 g, 0.80 mmol) and bis-
(triphenylphosphine)palladium(II) chloride (0.010 g, 0.018
mmol) in dry THF (3 mL) under argon was added hydride 3
(0.34 g, 0.80 mmol), and the mixture was stirred at room
temperature for 2 h. Then, the solvent was distilled off under
reduced pressure. The 119Sn NMR spectrum of the crude
product showed a mixture of two compounds: (E)-â-3-tripty-
cyldimethylstannyl-2-propen-1-ol (14; 67%) and R-2-tripty-
cyldimethylstannyl-2-propen-1-ol (15; 33%). Column chroma-
tography (silica gel 60) of the mixture afforded 14 (yield 0.19
g (0.41 mmol, 52%): mp 70-72 °C) and 15 (yield 0.10 g (0.22
mmol, 28%); mp 174-176 °C) in the fractions eluted with 96:4
and 93:7 hexane-diethyl ether, respectively. NMR spectra,
physical characteristics, and other analytical data of adducts
12-15 are included in the Supporting Information.
Stille Coupling Reaction: Synthesis of Methyl 2-Phe-
nylpropenoate (16). To a mixture of bromobenzene (0.12 g,
0.74 mmol), PdCl2(PPh3)2 (0.011 g, 2%), and some crystals of
2,6-di-tert-butyl-4-methylphenol under argon was added a
solution of 8 (0.39 g, 0.81 mmol) in dry toluene (2 mL) at room
temperature, and this mixture was stirred for 24 h under
reflux, with monitoring by TLC. Column chromatography on
silica gel 60 of the crude product gave compound 16 (0.079 g,
0.48 mmol, 65%)7,8 in the fraction eluted with 98:2 hexane-
diethyl ether.
6H, 2J(Sn,H) ) 53.8 Hz); 5.31 (s, 1H); 6.83-7.46 (m, 12H). 13
C
NMR (CDCl3): δ 1.08 (1J(Sn,C) ) 357.2 Hz); 58.17 (1J(Sn,C)
) 358.6 Hz); 54.46; 123.48; 124.23; 124.97; 125.43; 146.24;
147.13. 119Sn NMR (CDCl3): δ 84.9.
Synthesis of 9-Triptycyldimethyltin Hydride (3). To a
suspension of LiAlH4 (0.20 g, 4.97 mmol) in dry diethyl ether
(10 mL) under an atmosphere of argon at room temperature
was added dropwise a solution of 9-triptycyldimethyltin bro-
mide (2; 2.00 g, 4.14 mmol) in THF (60 mL). The mixture was
heated under reflux for 3 h. THF was evaporated and replaced
by diethyl ether, and then a saturated solution of NH4Cl was
added. The organic layer was separated, and the aqueous layer
was extracted three times with diethyl ether. The combined
organic extracts were dried over anhydrous MgSO4. Removal
of the solvent under reduced pressure gave 3: mp 218-220
°C; yield 1.45 g (3.59 mmol, 87%). 1H NMR (CDCl3): δ 0.57 (s,
6H, 2J(Sn,H) ) 53.0 Hz); 5.27 (s, 1H); 5.80 (m, 1H, 1J(119Sn,1H)
) 1804.0 Hz); 6.73-7.47 (m, 12H). 13C NMR (CDCl3): δ -9.96
(1J(Sn,C) ) 357.2 Hz); 67.46; 55.13; 123.98; 124.87; 125.02;
125.26; 147.91; 148.52. 119Sn NMR (CDCl3): δ -128.5.
Synthesis of Methyl (2R,3S)- and (2S,3R)-2,3-diphenyl-
3-triptycyldimethylstannylpropanoate (5). To a solution
of hydride 3 (0.38 g, 0.94 mmol) in dry toluene (1 mL) was
added a solution of methyl (E)-2,3-diphenylpropenoate (4; 0.22
g, 0.94 mmol) in toluene (1 mL) and a catalytic amount of
AIBN. The mixture was stirred for 24 h at 90 °C under an
argon atmosphere. The reaction was monitored by taking
samples at intervals and observing the disappearance of the
Sn-H absorption by IR. Then the solvent was removed under
reduced pressure and the crude product was purified by
column chromatography (silica gel 60). Compound 5 was
isolated in the fraction eluted with hexane-diethyl ether (98:
Iododestannylation Reaction: Synthesis of (Z)-1-Iodo-
1,2-diphenylethene (17). To a solution of 10 (0.24 g, 0.41
mmol) in dry CH2Cl2 (4.5 mL) under argon was added iodine
(0.12 g, 0.45 mmol). The mixture was stirred at room temper-
ature for 30 min, with monitoring of the reaction by TLC.
Column chromatography on silica gel 60 of the crude product
gave iodovinyl compound 17 in the fraction eluted with
hexane: yield 0.12 g (quantitative); mp 136-138 °C. 1H NMR
(CDCl3): δ 7.27-7.82 (m). 13C NMR (CDCl3): δ 102.02; 126.04;
126.17; 126.68; 126.96; 127.41; 127.69; 134.98; 138.24; 138.77.
1
2): mp 221-223 °C; yield 0.47 g (0.73 mmol, 78%). H NMR
(CDCl3): δ 0.52 (s, 3H, 2J(Sn,H) ) 49.6 Hz); 0.58 (s, 3H,
3
2J(Sn,H) ) 49.6 Hz); 3.57 (s, 3H); 3.87 (d, 1H, J(H,H) ) 9.3,
3
3
2J(Sn,H) ) 59.9 Hz); 4.50 (d, 1H, J(H,H) ) 9.3, J(Sn,H) )
59.9 Hz); 5.18 (s, 1H); 6.61-7.41 (m, 22H). 13C NMR (CDCl3):
δ -6.13 (1J(Sn,C) ) 329.7 Hz); -4.23 (1J(Sn,C) ) 307.5 Hz);
39.91 (1J(Sn,C) ) 331.7 Hz); 52.49; 55.19 (2J(Sn,C) ) 16.0 Hz);
55.57; 57.69 (1J(Sn,C) ) 377.7 Hz); 123.87; 124.83; 125.09;
127.23; 128.38; 128.45; 128.70; 129.12 (3J(Sn,C) ) 23.9 Hz);
139.07 (3J(Sn,C) ) 42.6 Hz); 142.94 (2J(Sn,C) ) 28.5 Hz);
147.72; 175.13 (3J(Sn,CdO) ) 8.2 Hz).
Acknowledgment. This work was supported by the
CONICET (Capital Federal, Argentina), CIC (Buenos
Aires Province, Argentina), and Universidad Nacional
del Sur (Bah´ıa Blanca, Argentina). We acknowledge a
research grant from Fundacio´n Antorchas (Argentina).
The help of Prof. Jose´ Luis Mascaren˜as, University of
Santiago de Compostela (Spain), in connection with the
elemental analyses is acknowledged. A travel grant to
J.C.P. from the Alexander von Humboldt Foundation
and fellowships from the CONICET and DAAD (Ger-
many) to V.I.D. and from the CIC to D.C.G. are also
gratefully acknowledged.
Addition of 9-Triptycyldimethyltin Hydride (3) to
Substituted Alkynes under Radical Conditions. Typical
Procedure. A mixture of phenylethyne (0.076 g, 0.74 mmol),
hydride 3 (0.30 g, 0.74 mmol), and AIBN as a catalyst was
heated under argon at 60 °C for 1 h (this optimal time of
reaction and temperature was indicated by earlier experi-
ments, in which the reaction was monitored by taking samples
at intervals and observing the disappearance of the Sn-H
absorption by IR). The 1H, 13C, and 119Sn NMR spectra of the
crude product showed that it consisted of isomer (Z)-6 only.
Column chromatography (silica gel 60) of this product afforded
compound 6 (0.26 g, 0.52 mmol, 70%) in the fraction eluted
with hexane-diethyl ether (99:1): mp 153-155 °C. NMR
spectra, physical characteristics, and other analytical data of
Supporting Information Available: Characterization
data for the products including full 1H (Table 3) and 13C NMR
spectra (Table 4), as well as mass spectra and elemental
analyses of the isolated pure compounds. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM049104Z