An iron catalysed and visible-light mediated alkoxy radical generation is described, which allows... more An iron catalysed and visible-light mediated alkoxy radical generation is described, which allows for a chemoselective oxidative C(sp3)–H bond functionalization providing access to two sets of structurally divergent functionalities.
Proceedings of the National Academy of Sciences, 1999
Encapsulation complexes are reversibly formed assemblies in which small molecule guests are compl... more Encapsulation complexes are reversibly formed assemblies in which small molecule guests are completely surrounded by large molecule hosts. The assemblies are held together by weak intermolecular forces and are dynamic: they form and dissipate on time scales ranging from milliseconds to days—long enough for many interactions, even reactions, to take place within them. Little information is available on the exchange process, how guests get in and out of these complexes. Here we report that these events can be slow enough for conventional kinetic studies, and reactive intermediates can be detected. Guest exchange has much in common with familiar chemical substitution reactions, but differs in some respects: no covalent bonds are made or broken, the substrate is an assembly rather than a single molecule, and at least four molecules are involved in multiple rate-determining steps.
ABSTRACT The reaction of (2-methoxy-(R)-1-phenylethyl)((S)-1-phenylethyl)amine (1), which has bee... more ABSTRACT The reaction of (2-methoxy-(R)-1-phenylethyl)((S)-1-phenylethyl)amine (1), which has been used in asymmetric synthesis, with [Li-6]-n-butyllithium in large excess in diethyl-d(10) ether (DEE) at 20 degrees C results in the formation of a mixed complex between [Li-6]lithium (2-methoxy-(R)-1-phenylethyl)(2-([Li-6]-lithio)-(S)-1-phenylethyl)amide (2) and two [Li-6]-n-butyllithiums. The complex contains four Lithiums in an asymmetric environment, which is observed in the H-1 NMR spectrum by the appearance of four signals from the nonequivalent alpha-protons of the two complexed n-butyllithiums. The solution structure of this mixed complex is proposed to be a tetramer with a distorted cubanoid core, on the basis of H-1,H-1-NOESY, H-1,Li-6-HOESY, Li-6,Li-6-COSY, and Li-6,Li-6-EXSY spectroscopy.
ABSTRACT [1.1]Ferrocenophanyllithium (1) is shown by dynamic NMR (DNMR) and isotopic perturbation... more ABSTRACT [1.1]Ferrocenophanyllithium (1) is shown by dynamic NMR (DNMR) and isotopic perturbation to undergo a rapid intramolecular 1,12-proton transfer coupled with 1,12-lithium ion transfer. The first [C−H−C]- hydrogen bond previously reported to be present in 1 is shown by X-ray crystallography to be absent in the solid state. The 13C NMR spectrum of the bridge-labeled compound [1,12-13C2][1.1]ferrocenophanyl[1-6Li]lithium (6) in 2,5-dimethyltetrahydrofuran (DMTHF) displays a 1:1:1 triplet (1J(13C,6Li) = 4.0 Hz) showing that 6Li is bonded to C-1 and that 1 is monomeric. Transient nuclear Overhauser effects (tNOE's) measured in DEE-d10 in bridged monodeuterated 1 show that the bridges in 1 are syn and not anti to each other and that lithium is exo-coordinated to the anionic bridge carbon. The 1J(13C,1H) coupling constants show that the hybridization of the carbanionic carbon is intermediate between sp2 and sp3. Thus the solution and solid state structures of 1 are similar. UV−vis spectroscopy shows that 1 exists mainly as contact ion pairs (CIPs) in the temperature range −100 to +25 °C in THF, DMTHF, and diethyl ether (DEE). In dimethoxyethane (DME), 1 is mainly CIPs above +25 °C but is mainly separated ion pairs (SIPs) below −30 °C.
Abstract Three chiral cis -octahedral Grignard reagents have been synthesized and structurally ch... more Abstract Three chiral cis -octahedral Grignard reagents have been synthesized and structurally characterized by X-ray diffraction methods. Crystals of cis -[( n -Pr)MgBr(dme) 2 ] ( 1 ), cis -[( i -Pr)MgBr(dme) 2 ] ( 2 ) and cis -[(allyl)MgBr(dme) 2 ] ( 3 ) were prepared from neat 1,2-dimethoxyethane (DME) and are all racemic. Synthesis and structural characterization of trans -[MgBr 2 (tmeda) 2 ] ( 4 ) and cis -[MgBr 2 (dme) 2 ] ( 5 ) indicated that bidentate tertiary amino ligands may be less well suited for the preparation of cis -octahedral Grignard reagents. On the other hand, the crystal structures of cis -[MgBr 2 (trigly)] ( 6 ) and [Mg 2 (μ-Br) 2 (trigly) 2 ][Mg 2 (μ-Me) 2 Br 4 ] ( 7 ) {trigly=triglyme)}, suggest that the triglyme ligand may be ideally suited for this purpose.
The SmI2/H2O/pyrrolidine mediated cleavage of benzylic alcohols and benzyl groups was studied and... more The SmI2/H2O/pyrrolidine mediated cleavage of benzylic alcohols and benzyl groups was studied and found to be a viable alternative to the Birch reduction yielding the corresponding deoxygenated product in excellent yield. The reaction has been investigated by kinetic methods, and a mechanism involving a pre-complexation of the alcohol to SmI2 followed by an amine mediated electron transfer and subsequent bond cleavage and transfer of a second electron and proton to yield the toluene product has been proposed. The reaction is strongly inhibited at higher concentrations of water, indicating that it proceeds via an inner-sphere electron transfer from samarium(II) to the benzyl group, and excess of water prevents coordination of benzyl alcohol to samarium.
A novel combination of SmI(2), KHMDS, and TsCN can be utilized to introduce a cyano group into st... more A novel combination of SmI(2), KHMDS, and TsCN can be utilized to introduce a cyano group into structurally diverse and highly sensitive 2-alkyl-chroman-4-ones. Subsequent oxidation allows the formed 2-alkyl-3-cyanochromones to be isolated in yields ranging from 49 to 77%. In addition, alpha-bromoketones and esters were found to undergo equally effective alpha-cyanation.
An iron catalysed and visible-light mediated alkoxy radical generation is described, which allows... more An iron catalysed and visible-light mediated alkoxy radical generation is described, which allows for a chemoselective oxidative C(sp3)–H bond functionalization providing access to two sets of structurally divergent functionalities.
Proceedings of the National Academy of Sciences, 1999
Encapsulation complexes are reversibly formed assemblies in which small molecule guests are compl... more Encapsulation complexes are reversibly formed assemblies in which small molecule guests are completely surrounded by large molecule hosts. The assemblies are held together by weak intermolecular forces and are dynamic: they form and dissipate on time scales ranging from milliseconds to days—long enough for many interactions, even reactions, to take place within them. Little information is available on the exchange process, how guests get in and out of these complexes. Here we report that these events can be slow enough for conventional kinetic studies, and reactive intermediates can be detected. Guest exchange has much in common with familiar chemical substitution reactions, but differs in some respects: no covalent bonds are made or broken, the substrate is an assembly rather than a single molecule, and at least four molecules are involved in multiple rate-determining steps.
ABSTRACT The reaction of (2-methoxy-(R)-1-phenylethyl)((S)-1-phenylethyl)amine (1), which has bee... more ABSTRACT The reaction of (2-methoxy-(R)-1-phenylethyl)((S)-1-phenylethyl)amine (1), which has been used in asymmetric synthesis, with [Li-6]-n-butyllithium in large excess in diethyl-d(10) ether (DEE) at 20 degrees C results in the formation of a mixed complex between [Li-6]lithium (2-methoxy-(R)-1-phenylethyl)(2-([Li-6]-lithio)-(S)-1-phenylethyl)amide (2) and two [Li-6]-n-butyllithiums. The complex contains four Lithiums in an asymmetric environment, which is observed in the H-1 NMR spectrum by the appearance of four signals from the nonequivalent alpha-protons of the two complexed n-butyllithiums. The solution structure of this mixed complex is proposed to be a tetramer with a distorted cubanoid core, on the basis of H-1,H-1-NOESY, H-1,Li-6-HOESY, Li-6,Li-6-COSY, and Li-6,Li-6-EXSY spectroscopy.
ABSTRACT [1.1]Ferrocenophanyllithium (1) is shown by dynamic NMR (DNMR) and isotopic perturbation... more ABSTRACT [1.1]Ferrocenophanyllithium (1) is shown by dynamic NMR (DNMR) and isotopic perturbation to undergo a rapid intramolecular 1,12-proton transfer coupled with 1,12-lithium ion transfer. The first [C−H−C]- hydrogen bond previously reported to be present in 1 is shown by X-ray crystallography to be absent in the solid state. The 13C NMR spectrum of the bridge-labeled compound [1,12-13C2][1.1]ferrocenophanyl[1-6Li]lithium (6) in 2,5-dimethyltetrahydrofuran (DMTHF) displays a 1:1:1 triplet (1J(13C,6Li) = 4.0 Hz) showing that 6Li is bonded to C-1 and that 1 is monomeric. Transient nuclear Overhauser effects (tNOE's) measured in DEE-d10 in bridged monodeuterated 1 show that the bridges in 1 are syn and not anti to each other and that lithium is exo-coordinated to the anionic bridge carbon. The 1J(13C,1H) coupling constants show that the hybridization of the carbanionic carbon is intermediate between sp2 and sp3. Thus the solution and solid state structures of 1 are similar. UV−vis spectroscopy shows that 1 exists mainly as contact ion pairs (CIPs) in the temperature range −100 to +25 °C in THF, DMTHF, and diethyl ether (DEE). In dimethoxyethane (DME), 1 is mainly CIPs above +25 °C but is mainly separated ion pairs (SIPs) below −30 °C.
Abstract Three chiral cis -octahedral Grignard reagents have been synthesized and structurally ch... more Abstract Three chiral cis -octahedral Grignard reagents have been synthesized and structurally characterized by X-ray diffraction methods. Crystals of cis -[( n -Pr)MgBr(dme) 2 ] ( 1 ), cis -[( i -Pr)MgBr(dme) 2 ] ( 2 ) and cis -[(allyl)MgBr(dme) 2 ] ( 3 ) were prepared from neat 1,2-dimethoxyethane (DME) and are all racemic. Synthesis and structural characterization of trans -[MgBr 2 (tmeda) 2 ] ( 4 ) and cis -[MgBr 2 (dme) 2 ] ( 5 ) indicated that bidentate tertiary amino ligands may be less well suited for the preparation of cis -octahedral Grignard reagents. On the other hand, the crystal structures of cis -[MgBr 2 (trigly)] ( 6 ) and [Mg 2 (μ-Br) 2 (trigly) 2 ][Mg 2 (μ-Me) 2 Br 4 ] ( 7 ) {trigly=triglyme)}, suggest that the triglyme ligand may be ideally suited for this purpose.
The SmI2/H2O/pyrrolidine mediated cleavage of benzylic alcohols and benzyl groups was studied and... more The SmI2/H2O/pyrrolidine mediated cleavage of benzylic alcohols and benzyl groups was studied and found to be a viable alternative to the Birch reduction yielding the corresponding deoxygenated product in excellent yield. The reaction has been investigated by kinetic methods, and a mechanism involving a pre-complexation of the alcohol to SmI2 followed by an amine mediated electron transfer and subsequent bond cleavage and transfer of a second electron and proton to yield the toluene product has been proposed. The reaction is strongly inhibited at higher concentrations of water, indicating that it proceeds via an inner-sphere electron transfer from samarium(II) to the benzyl group, and excess of water prevents coordination of benzyl alcohol to samarium.
A novel combination of SmI(2), KHMDS, and TsCN can be utilized to introduce a cyano group into st... more A novel combination of SmI(2), KHMDS, and TsCN can be utilized to introduce a cyano group into structurally diverse and highly sensitive 2-alkyl-chroman-4-ones. Subsequent oxidation allows the formed 2-alkyl-3-cyanochromones to be isolated in yields ranging from 49 to 77%. In addition, alpha-bromoketones and esters were found to undergo equally effective alpha-cyanation.
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Papers by Göran Hilmersson