Abstract
Facile carbon-tin bond activation in the reaction of 2-(trimethylstannyl) pyridine (1) with the organolanthanide complexes Cp*2LaCH(TMS) 2 (2a) and [Cp*2LaH]2 (2b) yields Cp*2La(2-pyridyl) (3), as well as Me3SnCH(TMS) 2 and Me3SnH, respectively. At room temperature, ethylene then undergoes insertion into the resulting La-C(pyridyl) bond followed by carbostannolysis to catalytically generate 2-(2-(Me3Sn)ethyl)pyridine (4) or, with extended reaction times, 6-ethyl-2-(2-(trimethylstannyl)ethyl) pyridine (5). In contrast to 1, 6-methyl-2-(trimethylstannyl)pyridine (6) is unreactive, likely reflecting steric constraints. With terminal alkynes, this catalytic heterocycle-SnMe3 activation/carbostannylation process affords tin-functionalized conjugated enynes. Thus, at 60 C 2b catalyzes the conversion 1 + 1-hexyne to yield (E)-2-butyl-1-(Me3Sn)-oct-1-en-3-yne in a 60:1 ratio E:Z isomer ratio. This reaction is available to α-monosubstituted and α-disubstituted terminal alkynes, while α-trisubstituted alkynes are too hindered for reaction. The catalytic cycle is proposed to proceed via a spectroscopically detectable Me 3Sn-alkynyl intermediate which undergoes insertion into a Cp*2La-alkynyl bond to produce the conjugated alkynyl product, which is subsequently protonolyzed from the Cp*2La center by a new terminal alkyne substrate molecule. NMR spectroscopic and kinetic data support the proposed pathway and indicate turnover-limiting alkyne insertion.
| Original language | English |
|---|---|
| Pages (from-to) | 1317-1327 |
| Number of pages | 11 |
| Journal | Organometallics |
| Volume | 32 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - Mar 11 2013 |
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ASJC Scopus subject areas
- Organic Chemistry
- Physical and Theoretical Chemistry
- Inorganic Chemistry
Cite this
Carbostannolysis mediated by bis(pentamethylcyclopentadienyl)lanthanide catalysts. Utility in accessing organotin synthons. / Wobser, Stephen D.; Stephenson, Casey J.; Delferro, Massimiliano; Marks, Tobin J.
In: Organometallics, Vol. 32, No. 5, 11.03.2013, p. 1317-1327.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Carbostannolysis mediated by bis(pentamethylcyclopentadienyl)lanthanide catalysts. Utility in accessing organotin synthons
AU - Wobser, Stephen D.
AU - Stephenson, Casey J.
AU - Delferro, Massimiliano
AU - Marks, Tobin J
PY - 2013/3/11
Y1 - 2013/3/11
N2 - Facile carbon-tin bond activation in the reaction of 2-(trimethylstannyl) pyridine (1) with the organolanthanide complexes Cp*2LaCH(TMS) 2 (2a) and [Cp*2LaH]2 (2b) yields Cp*2La(2-pyridyl) (3), as well as Me3SnCH(TMS) 2 and Me3SnH, respectively. At room temperature, ethylene then undergoes insertion into the resulting La-C(pyridyl) bond followed by carbostannolysis to catalytically generate 2-(2-(Me3Sn)ethyl)pyridine (4) or, with extended reaction times, 6-ethyl-2-(2-(trimethylstannyl)ethyl) pyridine (5). In contrast to 1, 6-methyl-2-(trimethylstannyl)pyridine (6) is unreactive, likely reflecting steric constraints. With terminal alkynes, this catalytic heterocycle-SnMe3 activation/carbostannylation process affords tin-functionalized conjugated enynes. Thus, at 60 C 2b catalyzes the conversion 1 + 1-hexyne to yield (E)-2-butyl-1-(Me3Sn)-oct-1-en-3-yne in a 60:1 ratio E:Z isomer ratio. This reaction is available to α-monosubstituted and α-disubstituted terminal alkynes, while α-trisubstituted alkynes are too hindered for reaction. The catalytic cycle is proposed to proceed via a spectroscopically detectable Me 3Sn-alkynyl intermediate which undergoes insertion into a Cp*2La-alkynyl bond to produce the conjugated alkynyl product, which is subsequently protonolyzed from the Cp*2La center by a new terminal alkyne substrate molecule. NMR spectroscopic and kinetic data support the proposed pathway and indicate turnover-limiting alkyne insertion.
AB - Facile carbon-tin bond activation in the reaction of 2-(trimethylstannyl) pyridine (1) with the organolanthanide complexes Cp*2LaCH(TMS) 2 (2a) and [Cp*2LaH]2 (2b) yields Cp*2La(2-pyridyl) (3), as well as Me3SnCH(TMS) 2 and Me3SnH, respectively. At room temperature, ethylene then undergoes insertion into the resulting La-C(pyridyl) bond followed by carbostannolysis to catalytically generate 2-(2-(Me3Sn)ethyl)pyridine (4) or, with extended reaction times, 6-ethyl-2-(2-(trimethylstannyl)ethyl) pyridine (5). In contrast to 1, 6-methyl-2-(trimethylstannyl)pyridine (6) is unreactive, likely reflecting steric constraints. With terminal alkynes, this catalytic heterocycle-SnMe3 activation/carbostannylation process affords tin-functionalized conjugated enynes. Thus, at 60 C 2b catalyzes the conversion 1 + 1-hexyne to yield (E)-2-butyl-1-(Me3Sn)-oct-1-en-3-yne in a 60:1 ratio E:Z isomer ratio. This reaction is available to α-monosubstituted and α-disubstituted terminal alkynes, while α-trisubstituted alkynes are too hindered for reaction. The catalytic cycle is proposed to proceed via a spectroscopically detectable Me 3Sn-alkynyl intermediate which undergoes insertion into a Cp*2La-alkynyl bond to produce the conjugated alkynyl product, which is subsequently protonolyzed from the Cp*2La center by a new terminal alkyne substrate molecule. NMR spectroscopic and kinetic data support the proposed pathway and indicate turnover-limiting alkyne insertion.
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U2 - 10.1021/om301031e
DO - 10.1021/om301031e
M3 - Article
VL - 32
SP - 1317
EP - 1327
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 5
ER -