The Experts below are selected from a list of 2931 Experts worldwide ranked by ideXlab platform
Janine Cossy - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of omega hydroxy ketones from omega benzyloxy weinreb amides by using a chemoselective nucleophilic addition Birch Reduction process
Organic Letters, 2004Co-Authors: Catherine Taillier, Veronique Bellosta, Christophe Meyer, Janine CossyAbstract:A chemoselective nucleophilic addition/Birch Reduction process applied to ω-benzyloxy Weinreb amides led to ω-hydroxy ketones in good yields.
-
synthesis of omega hydroxy ketones from omega benzyloxy weinreb amides by using a chemoselective nucleophilic addition Birch Reduction process
Organic Letters, 2004Co-Authors: Catherine Taillier, Veronique Bellosta, Christophe Meyer, Janine CossyAbstract:[reaction: see text] A chemoselective nucleophilic addition/Birch Reduction process applied to omega-benzyloxy Weinreb amides led to omega-hydroxy ketones in good yields.
Arthur G Schultz - One of the best experts on this subject based on the ideXlab platform.
-
the asymmetric Birch Reduction and Reduction alkylation strategies for synthesis of natural products
ChemInform, 1999Co-Authors: Arthur G SchultzAbstract:Synthetic applications of the asymmetric Birch Reduction and Reduction–alkylation are reported. Synthetically useful chiral intermediates have been obtained from chiral 2-alkoxy-, 2-alkyl-, 2-aryl- and 2-trialkylsilyl-benzamides I and the pyrrolobenzodiazepine-5,11-diones II. The availability of a wide range of substituents on the precursor benzoic acid derivative, the uniformly high degree of diastereoselection in the chiral enolate alkylation step, and the opportunity for further development of stereogenic centers by way of olefin addition reactions make this method unusually versatile for the asymmetric synthesis of natural products and related materials.
-
Asymmetric synthesis of the core structure of the Melodinus alkaloids
Tetrahedron Letters, 1999Co-Authors: Arthur G Schultz, Mingshi DaiAbstract:Abstract The strategy developed for an asymmetric synthesis of (+)-meloscine ( 1 ) features an early incorporation of the aromatic ring in 1 as the 5-benzyl substituent in 2 . The highly diastereoselective Birch Reduction-alkylation 2 → 3 , the unraveling of 3 to the butyrolactone carboxylic acid 7 , and the Mannich cyclization 9c → 10c are the key steps in the synthesis of the core tricyclic unit in 1 .
-
preparation and diastereoselective Birch Reduction alkylation of chiral 3 4 dihydro 1 2h isoquinolinones enantiospecific syntheses and opioid receptor affinities of several hydro 2 3 dimethyl 1h 7 12a methanobenzo 6 7 cycloocta 1 2 c pyridine 9 ols
Journal of Organic Chemistry, 1998Co-Authors: Arthur G Schultz, Timothy J Guzi, Erika Larsson, Rainer Rahm, Kshitij Thakkar, Jean M BidlackAbstract:Synthetic procedures have been developed to provide 2,3-disubstituted-3,4-dihydro-1(2H)-isoquinolinones 6, 10, and 15 from (1R,2S)-ephedrine, (1R,2R)-pseudoephedrine, and l-phenylalanine. Birch Reduction of 6 and 10 gave enantiomerically related lactam enolates that were alkylated with methyl iodide, allyl bromide, benzyl bromide, p-benzyloxybenzyl bromide, and p-methoxybenzyl bromide to give 7a−7e, 11a, and 11b with diastereoselectivities > 20:1. Birch Reduction−methylation of 15 gave 19 with a diastereoselectivity of >35:1. Selective Reduction of the disubstituted double bond in 19 with diimide and cleavage of the tert-butyldimethylsilyl ether gave 20b, from which iodoetherification under thermodynamic control gave the iodopyran 21a; iodoetherification of 20b under kinetic control gave the iodotetrahydrofuran 22. Enantiospecific syntheses of analogues of 24 (Schultz, A. G.; Kirincich, S. J.; Rahm, R. Tetrahedron Lett. 1995, 36, 4551−4554) have been developed. Tetracycle 24 is isomeric with the potent an...
-
asymmetric total synthesis of apovincamine and a formal synthesis of vincamine demonstration of a practical asymmetric linkage between aromatic carboxylic acids and chiral acyclic substrates
Journal of Organic Chemistry, 1997Co-Authors: Arthur G Schultz, William P Malachowski, You PanAbstract:Asymmetric syntheses of (+)-apovincamine (1a) and (+)-vincamine (2) are described. Construction of the pentacyclic diene lactam 14, a pivotal intermediate for synthesis of the cis-fused vincane-type alkaloids, began by Birch Reduction−alkylation of the chiral benzamide 3 to give the 6-ethyl-1-methoxy-4-methyl-1,4-cyclohexadiene 4. Conversion of 4 to 2,5-cyclohexadienone 5 (92% overall yield from 3) and HPLC analysis of 5 demonstrated the diastereomeric purity resulting from the Birch Reduction−alkylation to be >100:1. Dienone 5 was converted to butyrolactone 9 (47% overall yield from 3), and 9 was coupled with tryptamine (10) to give the amide 11a. Amido keto aldehyde 13 was obtained from 11a, and acid-catalyzed tricyclization and subsequent base-induced elimination of MeOH provided the desired cis-fused pentacyclic diene lactam 14. Examination of the two-step process 13 → 14 revealed a novel base-induced epimerization at C(21) which served to interconvert 14 and 17, possibly by the involvement of a homoe...
-
Birch Reduction and Reduction-alkylations of 3,4-dihydro-3-methyl-8-phenylisocoumarin
Tetrahedron Letters, 1996Co-Authors: Arthur G SchultzAbstract:Birch Reduction and Reduction-alkylations of 4 provide 3-methyl-8-phenyl-3,4,5,6,7,8-hexahydroisocoumarin 6 (88% yield) and a series of 8a-substituted-3-methyl-8-phenyl-3,4,6,7,8,8a-hexahydroisocoumarins 5a-d (84–89%). Conversions of 5a and 6 to cyclohexenones 12 and 13, and 6 to butadiene carboxylic acid 14 also are described.
William P Malachowski - One of the best experts on this subject based on the ideXlab platform.
-
catalytic enantioselective Birch heck sequence for the synthesis of tricyclic structures with all carbon quaternary stereocenters
Organic Letters, 2018Co-Authors: Andrew T Krasley, William P Malachowski, Hannah M Terz, Sabrina Tran TienAbstract:A new enantioselective desymmetrizing Mizoroki–Heck reaction is reported. The process affords high yields and enantioselectivities of tricyclic structures containing all-carbon quaternary stereocenters. The substrates for the reaction are efficiently synthesized from Birch Reduction–alkylation of benzoic acid and benzoate esters.
-
enantioselective synthesis of decalin structures with all carbon quaternary centers via one pot sequential cope rauhut currier reaction
Tetrahedron Letters, 2014Co-Authors: Tina Morgan Ross, Sarah J Burke, William P MalachowskiAbstract:The first example of one-pot sequential Cope/Rauhut-Currier reactions are reported and used to make functionalized decalin structures with all-carbon quaternary stereocenters. The substrates for the new sequential reaction are generated through a six-step sequence including an enantioselective Birch Reduction-allylation reaction which makes the overall process asymmetric.
-
exploration of the enantioselective Birch cope sequence for the synthesis of carbocyclic quaternary stereocenters
Journal of Organic Chemistry, 2007Co-Authors: Tapas Paul, William P Malachowski, Jisun LeeAbstract:Quaternary stereocenters on a 2-cyclohexen-1-one ring are synthesized with good to excellent levels of enantioselectivity. The quaternary stereocenter is created through a new synthetic sequence involving three reactions: the enantioselective Birch Reduction-allylation, enol ether hydrolysis, and the Cope rearrangement. To illustrate the ability of the sequence to enantioselectively generate complex structures, a variety of substrates are described. Notably, the sequence works for the enantioselective generation of vicinal quaternary-tertiary stereocenters, the generation of congested arylic quaternary stereocenters, and hydroxyalkyl substituted quaternary stereocenters.
-
the enantioselective Birch cope sequence for the synthesis of carbocyclic quaternary stereocenters application to the synthesis of mesembrine
Organic Letters, 2006Co-Authors: Tapas Paul, William P Malachowski, Jisun LeeAbstract:A synthetic technique for generating carbocyclic quaternary stereocenters with exceptionally high levels of enantioselectivity is described. A sequence of three reactions, enantioselective Birch Reduction−allylation, enol ether hydrolysis, and Cope rearrangement, is used to stereoselectively generate chiral quaternary centers on a 2-cyclohexen-1-one ring. The products of the sequence are 4,4-disubstituted-2-carboxamide-2-cyclohexen-1-one structures which are versatile intermediates in complex natural product synthesis. An application of the sequence to the synthesis of (+)-mesembrine illustrates the utility of these intermediates.
-
sequential Birch Reduction allylation and cope rearrangement of o anisic acid derivatives
ChemInform, 2005Co-Authors: William P Malachowski, Marisha BanerjiAbstract:Abstract A new method for the construction of quaternary centers on cycloalkane rings is reported. The Cope rearrangement of 4-methyl-2-allyl-2-( N -pyrrolidinyl)-carboxamide-3-cyclohexenone yields 4-methyl-4-allyl-2-( N -pyrrolidinyl)-carboxamide-2-cyclohexenone in high yield. The rearrangement substrates are easily generated from Birch Reduction–allylation of o -anisic acid derivatives.
Timothy J. Donohoe - One of the best experts on this subject based on the ideXlab platform.
-
asymmetric synthesis of the fully elaborated pyrrolidinone core of oxazolomycin a
Organic Letters, 2012Co-Authors: Timothy J. Donohoe, Timothy J C Oriordan, Manuel Peifer, Christopher R Jones, Timothy J MilesAbstract:The asymmetric synthesis of the key pyrrolidinone core, including a highly elaborated exocyclic carbon chain, of the γ-lactam β-lactone antibiotic oxazolomycin A is described. Principal features include the Birch Reduction of an aromatic pyrrole nucleus, a late stage RuO4 catalyzed pyrrolidine oxidation, and a highly diastereoselective organocerium addition to an aldehyde.
-
rearrangement of pyrrolines derived from the Birch Reduction of electron deficient pyrroles radical ring expansion to substituted tetrahydropyridines
Chemical Communications, 2004Co-Authors: Peter Turner, Timothy J. Donohoe, Rick P C CousinsAbstract:Access to the synthetically important tetrahydropyridine motif has been achieved by radical rearrangement of pyrrolines obtained from the Birch Reduction of electron-deficient pyrroles.
-
silyl substituted furans in the stereoselective Birch Reduction
ChemInform, 2001Co-Authors: Timothy J. Donohoe, Jeanbaptiste Guillermin, Andrew A Calabrese, Daryl S WalterAbstract:Abstract Chiral derivatives of 3-silyl-2-furoic acid were prepared and subjected to a Birch reductive alkylation reaction. It was found that the presence of a silicon atom, ortho to the chiral auxiliary, enabled the synthesis of dihydrofurans with high levels of stereoselectivity. We believe that the silicon group is essential in order to control the geometry of the enolate formed in the Reduction regime. Remarkably, the partial Reduction conditions could be tailored so that the silicon is removed in situ, before the furan derived enolate is alkylated.
-
The partial Reduction of heterocycles: an alternative to the Birch Reduction
Tetrahedron Letters, 2000Co-Authors: Timothy J. Donohoe, Rakesh R Harji, Rick P C CousinsAbstract:The partial Reduction of a series of heterocycles in THF is described. By adding amine 3 as a proton source and naphthalene as an electron carrier, we were able to produce reductively alkylated pyrrolines and dihydrofurans in moderate to good yields. This reaction does not require liquid ammonia as a solvent, which may have interesting ramifications for large-scale synthesis. Moreover, we were also able to quench the Reduction reactions with an acid chloride so performing a reductive acylation reaction.
-
the stereoselective Birch Reduction of pyrroles
ChemInform, 1999Co-Authors: Timothy J. Donohoe, Paul M Guyo, Madeleine HelliwellAbstract:Abstract The Birch Reduction has been applied to electron-deficient pyrroles substituted with a chiral auxiliary at the C-2 position. Using either 8-phenylmenthol or trans -2-(α-cumyl)cyclohexanol (TCC) as auxiliaries, high levels of stereoselectivity were obtained. Moreover, the auxiliary could be removed using a high-yielding three-step sequence to furnish substituted dehydroproline derivatives with high enantiomeric purity. By choosing either (−)-8-phenylmenthol or (+)-TCC as an auxiliary either enantiomer of the dehydroproline product could be obtained.
Marek Stankevic - One of the best experts on this subject based on the ideXlab platform.
-
diastereoselective desymmetrization of diarylphosphinous acid borane amides under Birch Reduction
Organic and Biomolecular Chemistry, 2015Co-Authors: Marek StankevicAbstract:Treatment of diarylphosphinous acid-borane amides possessing chiral amido functionality with an alkali metal solution in liquid ammonia induced a preferential dearomatization of one aryl substituent at phosphorus leading to the formation of non-equimolar amounts of diastereomers. Diastereoselectivity of dearomatization depends strongly on the structure of a chiral auxiliary.
-
the reactivity of arylphosphorus acid amides under Birch Reduction conditions
ChemInform, 2013Co-Authors: Marek Stankevic, Adam Wlodarczyk, Damian NieckarzAbstract:Arylphosphorus acid amides undergo generally two processes under Birch Reduction conditions - Birch Reduction or cleavage of the P-aryl bond.
-
the reactivity of arylphosphorus acid amides under Birch Reduction conditions
European Journal of Organic Chemistry, 2013Co-Authors: Marek Stankevic, Adam Wlodarczyk, Damian NieckarzAbstract:Several classes of arylphosphorus acid amides have been tested in reactions with alkali metal solutions in liquid ammonia. The outcomes of such reactions depend on the structures of the starting materials. Generally, two processes – Birch Reduction or cleavage of the P–aryl bond – can be operative. Diarylphosphinic amides tend to undergo double Birch Reduction to afford bis(cyclohexadienyl)phosphinic amides.
-
Birch Reduction of aryldialkylphosphine boranes
Tetrahedron Letters, 2009Co-Authors: Marek Stankevic, Michal K PietrusiewiczAbstract:Abstract Aryldialkylphosphine–boranes undergo facile Birch-type Reduction to afford cyclohexadienyldialkylphosphine–boranes in high yields. Judicious choice of the metal and the reaction conditions allows for complete elimination of the undesired P–Ph bond cleavage.