5 research outputs found
Rh(II)-Catalyzed Reactions of Diazoesters with Organozinc Reagents
RhÂ(II)-catalyzed reactions of diazoesters
with organozinc reagents
are described. Diorganozinc reagents participate in reactions with
diazo compounds by two distinct, catalyst-dependent mechanisms. With
bulky diisopropylethyl acetate ligands, the reaction mechanism is
proposed to involve initial formation of a Rh-carbene and subsequent
carbozincation to give a zinc enolate. With Rh<sub>2</sub>(OAc)<sub>4</sub>, it is proposed that initial formation of an azine precedes
1,2-addition by an organozinc reagent. This straightforward route
to the hydrazone products provides a useful method for preparing chiral
quaternary α-aminoesters or pyrazoles via the Paul–Knorr
condensation with 1,3-diketones. Crossover and deuterium labeling
experiments provide evidence for the mechanisms proposed
Rh(II)-Catalyzed Reactions of Diazoesters with Organozinc Reagents
RhÂ(II)-catalyzed reactions of diazoesters
with organozinc reagents
are described. Diorganozinc reagents participate in reactions with
diazo compounds by two distinct, catalyst-dependent mechanisms. With
bulky diisopropylethyl acetate ligands, the reaction mechanism is
proposed to involve initial formation of a Rh-carbene and subsequent
carbozincation to give a zinc enolate. With Rh<sub>2</sub>(OAc)<sub>4</sub>, it is proposed that initial formation of an azine precedes
1,2-addition by an organozinc reagent. This straightforward route
to the hydrazone products provides a useful method for preparing chiral
quaternary α-aminoesters or pyrazoles via the Paul–Knorr
condensation with 1,3-diketones. Crossover and deuterium labeling
experiments provide evidence for the mechanisms proposed
Enantioselective Synthesis of Cyclobutanes via Sequential Rh-catalyzed Bicyclobutanation/Cu-catalyzed Homoconjugate Addition
Enantiomerically
enriched cyclobutanes are constructed by a three-component process
in which <i>t</i>-butyl (<i>E</i>)-2-diazo-5-arylpent-4-enoates
are treated with Rh<sub>2</sub>(<i>S</i>-NTTL)<sub>4</sub> to provide enantiomerically enriched bicyclobutanes, which can subsequently
engage in homoconjugate addition/enolate trapping sequence to give
densely functionalized cyclobutanes with high diastereoselectivity.
This three-component, two-catalyst procedure can be carried out in
a single flask. Rh<sub>2</sub>(<i>S</i>-NTTL)<sub>4</sub>-catalyzed reaction of <i>t</i>-butyl (<i>Z</i>)-2-diazo-5-phenylpent-4-enoate gives the Büchner cyclization
product in excellent enantioselectivity
Enantioselective Synthesis of Cyclobutanes via Sequential Rh-catalyzed Bicyclobutanation/Cu-catalyzed Homoconjugate Addition
Enantiomerically
enriched cyclobutanes are constructed by a three-component process
in which <i>t</i>-butyl (<i>E</i>)-2-diazo-5-arylpent-4-enoates
are treated with Rh<sub>2</sub>(<i>S</i>-NTTL)<sub>4</sub> to provide enantiomerically enriched bicyclobutanes, which can subsequently
engage in homoconjugate addition/enolate trapping sequence to give
densely functionalized cyclobutanes with high diastereoselectivity.
This three-component, two-catalyst procedure can be carried out in
a single flask. Rh<sub>2</sub>(<i>S</i>-NTTL)<sub>4</sub>-catalyzed reaction of <i>t</i>-butyl (<i>Z</i>)-2-diazo-5-phenylpent-4-enoate gives the Büchner cyclization
product in excellent enantioselectivity
Enantioselective Synthesis of Cyclobutanes via Sequential Rh-catalyzed Bicyclobutanation/Cu-catalyzed Homoconjugate Addition
Enantiomerically
enriched cyclobutanes are constructed by a three-component process
in which <i>t</i>-butyl (<i>E</i>)-2-diazo-5-arylpent-4-enoates
are treated with Rh<sub>2</sub>(<i>S</i>-NTTL)<sub>4</sub> to provide enantiomerically enriched bicyclobutanes, which can subsequently
engage in homoconjugate addition/enolate trapping sequence to give
densely functionalized cyclobutanes with high diastereoselectivity.
This three-component, two-catalyst procedure can be carried out in
a single flask. Rh<sub>2</sub>(<i>S</i>-NTTL)<sub>4</sub>-catalyzed reaction of <i>t</i>-butyl (<i>Z</i>)-2-diazo-5-phenylpent-4-enoate gives the Büchner cyclization
product in excellent enantioselectivity