The stereoselective construction of quaternary stereogenic centers is described that employs an allylic substitution through the intermediacy of a chiral carbamate leaving group. Five carbamates with two substituents at the allylic terminus combined with phenylcopper or n-butylcopper to provide alkenes in moderate to good yields and with moderate to high enantioselectivities at the newly created quaternary stereogenic center. The E-carbamate with methyl and cyclohexyl substituents at the gamma-terminus provided the highest yield (87%) and enantioselectivity (>99.9:0.1 er) of all the substitution patterns tested. The corresponding Z-carbamate gave the lowest enantioselectivity observed (80.0:20.0). Carbamates with other substituents (n-butyl and t-butyl) at the E-terminal position gave moderate yields and enantioselectivities of alkenes. Cinnamyl substrates also provided good yields of alkenes with moderate enantioselectivities. The origin of enantioselectivity is analyzed in the context of dimeric lithioheterocuprate structures.
Highly regioselective decarboxylative Claisen rearrangement reactions of diallyl 2-sulfonylmalonates
摘要:
The decarboxylative Claisen rearrangement of a range of substituted diallyl 2-sulfonylmalonates is described. The substrates are made by C-carboxylation of the corresponding allyl sulfonylacetates with allyl para-nitrophenyl carbonates. The reactions display a high degree of regioselectivity, with allylic substituents possessing electron-rich substituents at the allyl three-position rearranging preferentially. (C) 2007 Elsevier Ltd. All rights reserved.
(Cyclopentadienyl)ruthenium-Catalyzed Regio- and Enantioselective Decarboxylative Allylic Etherification of Allyl Aryl and Alkyl Carbonates
作者:Martina Austeri、David Linder、Jérôme Lacour
DOI:10.1002/adsc.201000696
日期:2010.12.17
thenium hexafluorophosphate [CpRu(η6-naphthalene)][PF6]} in combination with a pyridine oxazoline ligand efficiently catalyze the decarboxylative allylic rearrangement of allyl aryl carbonates. Good levels of regio- and enantioselectivity are obtained. Starting from enantioenriched secondary carbonates, the reaction is stereospecific and the corresponding allylic ethers are obtained with net retention
Regio- and Enantioselective Allylation of Phenols<i>via</i>Decarboxylative Allylic Etherification of Allyl Aryl Carbonates Catalyzed by (Cyclopentadienyl)ruthenium(II) Complexes and Pyridine-Hydrazone Ligands
作者:Léo Egger、Cecilia Tortoreto、Thierry Achard、David Monge、Abel Ros、Rosario Fernández、José M. Lassaletta、Jérôme Lacour
DOI:10.1002/adsc.201500534
日期:2015.10.12
(Cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate [CpRu(CH3CN)3][PF6] in combination with pyridine-hydrazone ligands efficiently catalyzes the asymmetric decarboxylative allylic rearrangement of allylarylcarbonates. Formation of CO bonds with high regio- and enantioselectivity ratios (up to 95:5 and 98% ee) is obtained. Good stereocontrol of the pseudotetrahedral geometry of the CpRu
Asymmetric Construction of Quaternary Stereogenic Centers via Auxiliary-Based SN2’ Reactions: A Case of 1,7-Relative Stereogenesis
作者:Scott E. Denmark、Lyndon K. Marble
DOI:10.3987/com-13-s(s)82
日期:——
The stereoselective construction of quaternary stereogenic centers is described that employs an allylic substitution through the intermediacy of a chiral carbamate leaving group. Five carbamates with two substituents at the allylic terminus combined with phenylcopper or n-butylcopper to provide alkenes in moderate to good yields and with moderate to high enantioselectivities at the newly created quaternary stereogenic center. The E-carbamate with methyl and cyclohexyl substituents at the gamma-terminus provided the highest yield (87%) and enantioselectivity (>99.9:0.1 er) of all the substitution patterns tested. The corresponding Z-carbamate gave the lowest enantioselectivity observed (80.0:20.0). Carbamates with other substituents (n-butyl and t-butyl) at the E-terminal position gave moderate yields and enantioselectivities of alkenes. Cinnamyl substrates also provided good yields of alkenes with moderate enantioselectivities. The origin of enantioselectivity is analyzed in the context of dimeric lithioheterocuprate structures.
Highly regioselective decarboxylative Claisen rearrangement reactions of diallyl 2-sulfonylmalonates
作者:Donald Craig、Mark I. Lansdell、Simon E. Lewis
DOI:10.1016/j.tetlet.2007.08.130
日期:2007.10
The decarboxylative Claisen rearrangement of a range of substituted diallyl 2-sulfonylmalonates is described. The substrates are made by C-carboxylation of the corresponding allyl sulfonylacetates with allyl para-nitrophenyl carbonates. The reactions display a high degree of regioselectivity, with allylic substituents possessing electron-rich substituents at the allyl three-position rearranging preferentially. (C) 2007 Elsevier Ltd. All rights reserved.