Intramolecular Carbolithiation Reactions Research Articles

Readily Accessible 1,2-Amino Ether Ligands for Enantioselective Intramolecular Carbolithiation

A new class of chiral 1,2-amino ether ligands, readily accessible from naturally occurring α-amino- or α-hydroxy acids, was found to provide high levels of both conversion and stereocontrol (up to 95:5 er) in intramolecular carbolithiation reactions, outperforming the benchmark ligand (-)-sparteine. The ligand could be used in a substoichiometric amount (0.25 equiv) without significant loss of enantioselectivity.

Synthesis of Tetrahydroquinolines through Intramolecular Carbolithiation Reactions

Synthesis of Tetrahydroquinolines through Intramolecular Carbolithiation Reactions

Intramolecular Carbolithiation Reactions in the Construction of Medium‐Sized Rings. Synthesis of Pyrroloisoquinolines, Benzazepines, and Benzazocines

AbstractMesityllithium (MesLi) was found to be superior to butyllithium for the formation of aryllithium intermediates by iodine–lithium exchange. Subsequent intramolecular carbolithiation of the 2‐alkenyl‐substituted ortho‐lithiated N‐benzylpyrroles proceeded efficiently when the alkene was substituted with an electron‐withdrawing group. The procedure is applicable to the construction of six‐, seven‐, and eight‐membered rings, thus, opening new routes to pyrroloisoquinolines, benzazepines, and benzazocines. Although the use of (–)‐sparteine as a chiral ligand led to low levels of enantioselection, enantiomerically pure isoquinolines could be synthesized by applying this protocol to the related pyrrolidines derived from proline, as the reactions proceeded with complete diastereoselectivity.

ChemInform Abstract: Intramolecular Carbolithiation Reactions for the Synthesis of 2,4‐Disubstituted Tetrahydroquinolines: Evaluation of TMEDA and (‐)‐Sparteine as Ligands in the Stereoselectivity.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Intramolecular Carbolithiation Reactions for the Synthesis of 2,4-Disubstituted Tetrahydro-quinolines: Evaluation of TMEDA and (−)-Sparteine as Ligands in the Stereoselectivity † Dedicated to Prof. Josep Font on the occasion of his 70th birthday.

The preparation of 4-substituted 2-phenyltetrahydroquinolines from N-alkenylsubstituted 2-iodoanilines via intramolecular carbolithiation reactions has been investigated. The stereochemical outcome of the carbolithiation reactions depends on the nature of organolithium employed to perform the lithium-halogen exchange, the solvent, or the use of additives, for example, TMEDA or chiral bidentated ligands such as (-)-sparteine. Thus, the 2,4-disubstituted tetrahydroquinolines are obtained with moderate diastereoselectivities (up to 77:23) and with ee up to 94% when Weinreb amide derivatives are used (R = CONMe(OMe)).

Intramolecular Carbolithiation of Aromatic N-Allyl-N-(2-Lithioallyl)Amines:Reinvestigation of the Mechanism and Synthesis of Functionalized Pyrrolidines

The intramolecular carbolithiation reactions of aromatic N-allyl-N-(2-lithioallyl)amines have been studied in detail. Although we have initially proposed a 6-endo ring closure for these substrates, we have found that the course of these processes starts with a 5-exo cyclization reaction. Interestingly, 3- functionalized-4-methylenepyrrolidines have been synthesized from simple starting materials. Keywords: pyrrolidines, 5-exo cyclizations, organolithiums, Carbolithiation reactions

Intramolecular carbolithiation of N-allyl- N-2-lithioallylamines: effect of the allyl moiety

The preparation of new N-2-bromoallyl- N-(3-functionalized)allylamines and the intramolecular carbolithiation reactions of the corresponding organolithiums generated by bromine–lithium exchange are reported. The effect of the substituent at the terminal position of the allyl moiety is studied. This methodology allows the efficient synthesis of a variety of interesting functionalized pyrrolidine and hexahydroindole derivatives from simple starting materials. To cite this article: J. Barluenga et al., C. R. Chimie 7 (2004) .

Intramolecular carbolithiation reactions for the preparation of 3-alkenylpyrrolidines.

Tin-lithium exchange allows the formation of alpha-amino-organolithium species that undergo anionic cyclization onto allylic ethers to give 3-alkenylpyrrolidines. The methodology has been applied to the synthesis of an advanced intermediate related to the natural product (-)-alpha-kainic acid.

Intramolecular carbolithiation reactions for the preparation of Azabicyclo

Tin-lithium exchange and intramolecular carbolithiation (anionic cyclization) have been used to construct the three nitrogen-positional isomers of the azabicyclo[2.2.1]heptane ring system. The 7-azabicyclo[2.2.1]heptane ring system is accessed from either diastereomer of a 2,5-disubstituted pyrrolidine, via a chiral organolithium intermediate. The 2-azabicyclo[2.2.1]heptane ring system is formed stereoselectively in low yield by a tandem cyclization, together with the product from monocyclization. Better yields of the 2-aza ring system can be obtained using an alternative approach from a 2-tributylstannyl-4-allylpyrrolidine, despite the trans arrangement of the tin (and, hence, lithium) atom and the allyl unit. The 1-azabicyclo[2.2.1]heptane ring system is accessed in just three steps from 4-piperidone.

ChemInform Abstract: Facile Intramolecular Carbolithiation Reactions of Alkylthio‐ and Alkoxyacetylenes by Stabilized Carbanions. A Novel Strategy for the Synthesis of Functionalized Carbocycles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Facile intramolecular carbolithiation reactions of alkylthio- and alkoxyacetylenes by stabilized carbanions. A novel strategy for the synthesis of functionalized carbocycles

Facile intramolecular carbolithiation reactions of alkylthio- and alkoxyacetylenes by stabilized carbanions. A novel strategy for the synthesis of functionalized carbocycles