126497-27-6

Usage

Uses

2-Cyclopentylidene-2-phenylacetic Acid is a glycopyrrolate impurity.

Upstream product

• 25209-52-3 α-(1-Hydroxycyclopentyl)phenylessigsaeure 
• 124-38-9 carbon dioxide 
• 57718-12-4 (6-iodohex-1-yn-1-yl)benzene 
• 103-82-2 phenylacetic acid 
• 120-92-3 cyclopentanone 
• 69936-53-4 6-phenylhex-5-yn-1-ol 
• 16664-48-5 6-bromo-1-phenyl-1-hexyne 
• 25118-60-9 1-phenylethynyl-cyclopentanol 
• 15206-55-0 methyl 2-oxo-2-phenylacetate 
• 427-49-6 2-cyclopentyl-2-hydroxy-2-phenylacetic acid 
• 4410-77-9 benzylidenecyclopentane 
• 591-50-4 iodobenzene 
• 10297-06-0 1-chloro-5-hexyne 

Downstream Products

• 1404453-67-3 3-(2-cyclopentylidene-2-phenylacetoxy)-1,1-dimethylpyrrolidinium bromide 
• 73495-21-3 (R)-2-cyclopentyl-2-phenylacetic acid 

Relevant academic research and scientific papers

Enantioselective Hydrogenation of Tetrasubstituted α,β-Unsaturated Carboxylic Acids Enabled by Cobalt(II) Catalysis: Scope and Mechanistic Insights

Chiral carboxylic acids are important compounds because of their prevalence in pharmaceuticals, natural products and agrochemicals. Asymmetric hydrogenation of α,β-unsaturated carboxylic acids has been widely recognized as one of the most efficient synthetic approaches to afford such compounds. Although related asymmetric hydrogenation of di- and trisubstituted unsaturated acids with noble metals is well established, asymmetric hydrogenation of challenging tetrasubstituted α,β-unsaturated carboxylic acids is rarely reported. We demonstrate enantioselective hydrogenation of cyclic and acyclic tetrasubstituted α,β-unsaturated carboxylic acids via cobalt(II) catalysis. This protocol showed broad substrate scope and gave chiral carboxylic acids in good yields with excellent enantiocontrol (up to 98 % yield and 99 % ee). Combined experimental and computational mechanistic studies support a CoII catalytic cycle involving migratory insertion and σ-bond metathesis processes. DFT calculations reveal that enantioselectivity may originate from the steric effect between the phenyl groups of the ligand and the substrate.

Stereospecific Electrophilic Fluorocyclization of α,β-Unsaturated Amides with Selectfluor

An efficient fluorocyclization of α,β-unsaturated amides through a formal halocyclization process is developed. The reaction proceeds under transition-metal-free conditions and leads to the formation of fluorinated oxazolidine-2,4-diones with excellent regio- and diastereoselectivity. The evaluation of the reaction mechanism based on preliminary experiments and density functional theory calculations suggests that a synergetic syn-oxo-fluorination occurs and is followed by an anti-oxo substitution reaction. The reaction opens a new window in the field of stereospecific fluorofunctionalization.

Ni-Catalyzed Carboxylation of Unactivated Alkyl Chlorides with CO2

A catalytic carboxylation of unactivated primary, secondary, and tertiary alkyl chlorides with CO2 at atmospheric pressure is described. This protocol represents the first intermolecular cross-electrophile coupling of unactivated alkyl chlorides, thus leading to new knowledge in the cross-coupling arena.

Ni-Catalyzed Divergent Cyclization/Carboxylation of Unactivated Primary and Secondary Alkyl Halides with CO2

A user-friendly Ni-catalyzed reductive cyclization/carboxylation of unactivated alkyl halides with CO2 is described. The protocol operates under mild conditions with an excellent chemoselectivity profile and a divergent syn/anti selectivity pat

Oxidative rearrangement of tertiary propargylic alcohols

An oxidative rearrangement of tertiary alcohols mediated by m-CPBA is described that generates tetrasubstituted alkenes with a carboxylic acid substituent. The mechanism of the reaction is proposed to proceed through epoxidation of the alkyne to form an o

Iridium-catalyzed enantioselective hydrogenation of α,β- unsaturated carboxylic acids with tetrasubstituted olefins

A highly efficient asymmetric hydrogenation of α,β-unsaturated carboxylic acids with tetrasubstituted olefin catalyzed by chiral spiro iridium complexes has been developed for the preparation of chiral α-substituted carboxylic acids in excellent enantioselectivities (up to 99% ee).

Carry over of impurities: A detailed exemplification for glycopyrrolate (NVA237)

The original synthesis of glycopyrrolate (NVA237) was revised and shortened into an essentially one-pot process. Without isolating the intermediates, their purification became obsolete, thereby increasing the possibility of the carry over of impurities. For that reason, the actual, potential, and theoretical impurities of the starting materials cyclopentyl mandelic acid and 1-methyl-pyrrolidin-3-ol as well as byproducts which may occur during the synthesis were thoroughly investigated; furthermore, their transformation to possible impurities in the drug substance along the new synthetic route was performed to exclude them as actual impurities in the drug substance with certainty. The question is raised how detailed such investigation-which are fairly manageable for a simple product like glycopyrrolate-need to be.

Silver-catalyzed regioselective carbomagnesiation of alkynes with alkyl halides and Grignard reagents

A silver-catalyzed carbomagnesiation of alkynes with alkyl halides and Grignard reagents afforded alkenyl Grignard reagents regioselectively, where the alkyl group of the alkyl halide, but not that of the Grignard reagent, was introduced into the alkyne.

Cyclization of acetylenic alkyllithiums

The scope and limitations of cyclization reactions involving acetylenic alkyllithiums, which were prepared at-78 °C by lithium-iodine exchange between the corresponding iodide and tert-butyllithium in a solution of n-pentane-diethyl ether (3:2 by volume), have been investigated. 4-Pentynyllithiums, 5-hexynyllithiums, and 6-heptynyllithiums bearing a phenyl or trimethylsilyl substituent on the triple bond undergo regiospecific exo-dig cyclization to give 4-, 5-, and 6-membered rings, respectively, bearing an exocyclic lithiomethylene moiety. Cyclization of the analogous alkyl-substituted acetylenic alkyllithiums seems to be confined to the 5-exo mode. The vinyllithium products of the cyclizations may be trapped by reaction with electrophiles to afford functionalized cycloalkylidene derivatives in good yield. The cyclization reactions were found to be highly stereoselective: intramolecular addition of the C-Li unit to the triple bond to produce 4- or 5-membered rings proceeds in a syn fashion to generate isomerically pure exocyclic vinyllithiums that may be functionalized to give stereoisomerically pure products. At the higher temperatures needed to effect cyclization of 6-heptynyllithiums, the initially formed (Z)-vinyllithium intermediate is isomerized to the more stable E-isomer which, when trapped with an electrophile, affords stereoisomerically pure product formally derived from anti addition to the triple bond.

PREPARATION AND FACILE CYCLIZATION OF 5-ALKYN-1-YLLITHIUMS

Primary 5-hexyn-1-yllithiums, which may be generated in virtually quantitative yield by low-temperature lithium-iodine interchange, undergo regiospecific 5-exo-dig cyclization via stereoselectively syn-addition of CH2Li to the alkyne moiety to give vinyllithiums that may be trapped with any of a variety of electrophiles to deliver functionalized cyclopentylidene-containing products.