Styrene cyclopropanation and ethyl diazoacetate dimerization catalyzed by ruthenium complexes containing chiral tridentate phosphine ligands

Hon Man Lee, Claudio Bianchini, Guochen Jia, Pierluigi Barbaro

Research output: Contribution to journalArticle

56 Citations (Scopus)

Abstract

Various five-coordinate ruthenium(II) complexes of the general formula RuCl2L, where L is a chiral triphosphine ligand, have been tested as catalyst precursors for the cyclopropanation of styrene using ethyl diazoacetate (EDA) as the carbene source. Some of the complexes investigated have been found to catalyze the cyclopropanation reaction, but the conversions to cyclopropanes and the diastereoselectivities were generally poor. With all the catalyst precursors investigated, the dimerization of ethyl diazoacetate to diethyl maleate or diethyl fumarate largely prevailed over cyclopropanation. The best performance was obtained with the complex RuCl2(ttp*) (2; ttp* = (S,S)-PhP(CH2CHMeCH2PPh2)2) which gave ca. 21% of cyclopropanes, 42% of olefins, and 1% of metathesis products. The highest enantiomeric excess was 35% for the (Z)-2-phenylcyclopropanecarboxylate. In the presence of silver triflate, 2 gave rise to a much more active and selective catalyst system, as the yield in cyclopropanation products increased up to 84%. Neither the regioselectivity nor the diastereoselectivity was appreciably improved, however. The carbene complexes RuCl2(ttp*)(=CHCO2Et) and RuCl2(ttp)(=CHCO2Et), where ttp is the achiral ligand PhP(CH2CH2CH2PPh2)2, were isolated and characterized by multinuclear NMR spectroscopy. These carbene complexes were found to react with an excess of ethyl diazoacetate to give exclusively diethyl maleate and diethyl fumarate in a 95:5 ratio. The selective formation of cyclopropanation products was conversely observed upon reaction with styrene in the presence of silver triflate. In the absence of a chloride scavenger, cyclopropanes were still formed together with an appreciable amount of the metathesis product PhHC=CHCO2Et.

Original languageEnglish
Pages (from-to)1961-1966
Number of pages6
JournalOrganometallics
Volume18
Issue number10
DOIs
Publication statusPublished - 1999 May 10

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phosphine
diethyl maleate
Cyclopropanes
Styrene
Ruthenium
Dimerization
dimerization
styrenes
phosphines
ruthenium
cyclopropane
carbenes
Ligands
maleates
ligands
Catalysts
metathesis
products
catalysts
Regioselectivity

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

Cite this

@article{c946d70b0af04a58b298969eb464723f,
title = "Styrene cyclopropanation and ethyl diazoacetate dimerization catalyzed by ruthenium complexes containing chiral tridentate phosphine ligands",
abstract = "Various five-coordinate ruthenium(II) complexes of the general formula RuCl2L, where L is a chiral triphosphine ligand, have been tested as catalyst precursors for the cyclopropanation of styrene using ethyl diazoacetate (EDA) as the carbene source. Some of the complexes investigated have been found to catalyze the cyclopropanation reaction, but the conversions to cyclopropanes and the diastereoselectivities were generally poor. With all the catalyst precursors investigated, the dimerization of ethyl diazoacetate to diethyl maleate or diethyl fumarate largely prevailed over cyclopropanation. The best performance was obtained with the complex RuCl2(ttp*) (2; ttp* = (S,S)-PhP(CH2CHMeCH2PPh2)2) which gave ca. 21{\%} of cyclopropanes, 42{\%} of olefins, and 1{\%} of metathesis products. The highest enantiomeric excess was 35{\%} for the (Z)-2-phenylcyclopropanecarboxylate. In the presence of silver triflate, 2 gave rise to a much more active and selective catalyst system, as the yield in cyclopropanation products increased up to 84{\%}. Neither the regioselectivity nor the diastereoselectivity was appreciably improved, however. The carbene complexes RuCl2(ttp*)(=CHCO2Et) and RuCl2(ttp)(=CHCO2Et), where ttp is the achiral ligand PhP(CH2CH2CH2PPh2)2, were isolated and characterized by multinuclear NMR spectroscopy. These carbene complexes were found to react with an excess of ethyl diazoacetate to give exclusively diethyl maleate and diethyl fumarate in a 95:5 ratio. The selective formation of cyclopropanation products was conversely observed upon reaction with styrene in the presence of silver triflate. In the absence of a chloride scavenger, cyclopropanes were still formed together with an appreciable amount of the metathesis product PhHC=CHCO2Et.",
author = "Lee, {Hon Man} and Claudio Bianchini and Guochen Jia and Pierluigi Barbaro",
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Styrene cyclopropanation and ethyl diazoacetate dimerization catalyzed by ruthenium complexes containing chiral tridentate phosphine ligands. / Lee, Hon Man; Bianchini, Claudio; Jia, Guochen; Barbaro, Pierluigi.

In: Organometallics, Vol. 18, No. 10, 10.05.1999, p. 1961-1966.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Styrene cyclopropanation and ethyl diazoacetate dimerization catalyzed by ruthenium complexes containing chiral tridentate phosphine ligands

AU - Lee, Hon Man

AU - Bianchini, Claudio

AU - Jia, Guochen

AU - Barbaro, Pierluigi

PY - 1999/5/10

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N2 - Various five-coordinate ruthenium(II) complexes of the general formula RuCl2L, where L is a chiral triphosphine ligand, have been tested as catalyst precursors for the cyclopropanation of styrene using ethyl diazoacetate (EDA) as the carbene source. Some of the complexes investigated have been found to catalyze the cyclopropanation reaction, but the conversions to cyclopropanes and the diastereoselectivities were generally poor. With all the catalyst precursors investigated, the dimerization of ethyl diazoacetate to diethyl maleate or diethyl fumarate largely prevailed over cyclopropanation. The best performance was obtained with the complex RuCl2(ttp*) (2; ttp* = (S,S)-PhP(CH2CHMeCH2PPh2)2) which gave ca. 21% of cyclopropanes, 42% of olefins, and 1% of metathesis products. The highest enantiomeric excess was 35% for the (Z)-2-phenylcyclopropanecarboxylate. In the presence of silver triflate, 2 gave rise to a much more active and selective catalyst system, as the yield in cyclopropanation products increased up to 84%. Neither the regioselectivity nor the diastereoselectivity was appreciably improved, however. The carbene complexes RuCl2(ttp*)(=CHCO2Et) and RuCl2(ttp)(=CHCO2Et), where ttp is the achiral ligand PhP(CH2CH2CH2PPh2)2, were isolated and characterized by multinuclear NMR spectroscopy. These carbene complexes were found to react with an excess of ethyl diazoacetate to give exclusively diethyl maleate and diethyl fumarate in a 95:5 ratio. The selective formation of cyclopropanation products was conversely observed upon reaction with styrene in the presence of silver triflate. In the absence of a chloride scavenger, cyclopropanes were still formed together with an appreciable amount of the metathesis product PhHC=CHCO2Et.

AB - Various five-coordinate ruthenium(II) complexes of the general formula RuCl2L, where L is a chiral triphosphine ligand, have been tested as catalyst precursors for the cyclopropanation of styrene using ethyl diazoacetate (EDA) as the carbene source. Some of the complexes investigated have been found to catalyze the cyclopropanation reaction, but the conversions to cyclopropanes and the diastereoselectivities were generally poor. With all the catalyst precursors investigated, the dimerization of ethyl diazoacetate to diethyl maleate or diethyl fumarate largely prevailed over cyclopropanation. The best performance was obtained with the complex RuCl2(ttp*) (2; ttp* = (S,S)-PhP(CH2CHMeCH2PPh2)2) which gave ca. 21% of cyclopropanes, 42% of olefins, and 1% of metathesis products. The highest enantiomeric excess was 35% for the (Z)-2-phenylcyclopropanecarboxylate. In the presence of silver triflate, 2 gave rise to a much more active and selective catalyst system, as the yield in cyclopropanation products increased up to 84%. Neither the regioselectivity nor the diastereoselectivity was appreciably improved, however. The carbene complexes RuCl2(ttp*)(=CHCO2Et) and RuCl2(ttp)(=CHCO2Et), where ttp is the achiral ligand PhP(CH2CH2CH2PPh2)2, were isolated and characterized by multinuclear NMR spectroscopy. These carbene complexes were found to react with an excess of ethyl diazoacetate to give exclusively diethyl maleate and diethyl fumarate in a 95:5 ratio. The selective formation of cyclopropanation products was conversely observed upon reaction with styrene in the presence of silver triflate. In the absence of a chloride scavenger, cyclopropanes were still formed together with an appreciable amount of the metathesis product PhHC=CHCO2Et.

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