James Taylor

• PhD
• PostDoc Position at University of St Andrews

The use of 2-carboxyphenylboronic acid (5 mol %) and oxalic acid (10 mol %) with 2-butanone as a solvent for the racemization of a range of enantiomerically pure secondary and tertiary alcohols is demonstrated. The process is postulated to proceed via reversible Brønsted acid-catalyzed C-O bond cleavage through an achiral carbocation intermediate.

The full scope and limitations of the catalytic acylative kinetic resolution of a range of tertiary heterocyclic alcohols (78 examples, s up to >200) is reported under operationally‐simple conditions, using low loadings of a commercially available Lewis basic isothiourea catalyst, HyperBTM (generally 1 mol %). The protocol is highly effective for t...

Enantiomerically pure alcohols and amines are ubiquitous throughout Nature and are found within numerous biologically active compounds. This chapter provides a comprehensive overview of strategies for the nonenzymatic acylative kinetic resolution and desymmetrization of alcohols and amines, which have emerged as powerful methods for the preparation...

The use of silyl nitronates is reported for the isothiourea-catalyzed synthesis of γ-nitro-substituted silyl esters containing up to two contiguous stereocenters in good yields with excellent enantioselectivities (up to 93% yield and 99:1 er). The serendipitously discovered formation of silyl ester products in this reaction demonstrates a novel pla...

An evaluation of a range of aryl, alkyl and vinyl esters as prospective C(1)-ammonium enolate precursors in enantioselective Michael addition-lactonisation processes with (E)-trifluoromethylenones using isothiourea catalysis is reported. Electron deficient aryl esters are required for reactivity, with 2,4,6-trichlorophenyl esters providing optimal...

Catalytic enantioselective functionalization of 2-pyrrolyl acetic acid with trichloromethyl enones using isothiourea catalysis is reported, leading to a range of stereodefined diesters and diamides after nucleophilic ring opening with either methanol or benzylamine (30 examples, up to >95:5 dr and >99:1 er). Subsequent intramolecular Friedel–Crafts...

The suitability of using the selectivity factor, s, as a metric for kinetic resolution reactions and the errors associated with its measurement are considered. Investigation of the analytical error associated with HPLC analysis of a kinetic resolution reveals that one of the largest potential sources of variation arises from the ability of a practi...

The scope and limitations of a photoinitiated N- to C-sulfonyl migration process within a range of dihydropyridinones is assessed. This sulfonyl transfer proceeds without erosion of either diastereo- or enantiocontrol, and is general across a range of N-sulfonyl substituents (SO2R; R = Ph, 4-MeC6H4, 4-MeOC6H4, 4-NO2C6H4, Me, Et) as well as C(3)-(ar...

A tandem relay catalytic protocol using both Pd and isothiourea catalysis has been developed for the enantioselective synthesis of α-amino acid derivatives containing two stereogenic centers from readily accessible N,N-disubstituted glycine aryl esters and allylic phosphates. The optimized process uses a bench-stable succinimide-based Pd-precatalys...

A mechanistic study of the isothiourea-catalysed enantioselective [2,3]-rearrangement of allylic ammonium ylides is described. Reaction kinetic analyses using 19F NMR and density functional theory computations have elucidated a reaction profile and allowed identification of the catalyst resting state and turnover-rate limiting step. A catalytically...

N-Heterocyclic carbene (NHC)-catalysed redox [4+2]-hetero-Diels-Alder reactions of α-aroyloxyaldehydes with either β,γ-unsaturated α-ketoesters or α,β-unsaturated γ-ketoesters generates substituted syn-dihydropyranones in good yield with excellent enantioselectivity (up to >99:1 er). The product diastereoselectivity is markedly dependent upon the n...

Supplementary

α,β-Unsaturated acyl ammoniums generated from the reaction of α,β-unsaturated 2,4,6-trichlorophenol (TCP) esters bearing a pendent enone with an isothiourea organocatalyst are versatile intermediates in a range of enantioselective nucleophile-dependent domino processes to form complex products of diverse topology with excellent stereoselectivity. U...

N-Acyl imidazoles and catalytic isothiourea hydrochloride salts function as ammonium enolate precursors in the absence of base. Enantioselective Michael addition–cyclization reactions using different α,β-unsaturated Michael acceptors have been performed to form dihydropyranones and dihydropyridinones with high stereoselectivity. Detailed mechanisti...

N-Acyl imidazoles and catalytic isothiourea hydrochloride salts function as ammonium enolate precursors in the absence of base. Enantioselective Michael addition–cyclization reactions using different α,β-unsaturated Michael acceptors have been performed to form dihydropyranones and dihydropyridinones with high stereoselectivity. Detailed mechanisti...

The catalytic enantioselective synthesis of a range of cis-pyrrolizine carboxylate derivatives with outstanding stereocontrol (14 examples, >95 : 5 dr, >98 : 2 er) through an isothiourea-catalyzed intramolecular Michael addition-lactonisation and ring-opening approach from the corresponding enone acid is reported. An optimised and straightforward t...

The title process is investigated with racemic oxaziridine (II) under conditions A).

Hydrazone-carboxylic acids undergo intramolecular cyclization in the presence of pivaloyl chloride, iPr2NEt, and catalytic DABCO to form a range of substituted fused tricyclic 2,3-dihydro-1,3,4-oxadiazoles in high yields.

[2,3]-Sigmatropic rearrangement processes of allylic ylides or their equivalents can be applied to a variety of different substrates and generate products of wide interest/applicability to organic synthesis. This review describes the development and applications of stereoselective [2,3]-rearrangement reactions in which a substoichiometric amount of...

alpha,beta-Unsaturated trichloromethyl ketones are suitable a alpha,beta-unsaturated amide and ester equivalents in N-heterocyclic carbene (NHC)-catalyzed redox hetero-Diels Alder reactions with azolium enolates generated from alpha-aroyloxyaldehydes. The initially formed syn-dihydropyranone products can be isolated or can undergo ring-opening with...

A highly enantioselective Lewis base-catalysed formal [3+2] cycloaddition of ammonium enolates and oxaziridines to give stereodefined oxazolidin-4-ones in high yield is described. Employing an enantioenriched oxaziridine in this process leads to a matched/mis-matched effect with the isothiourea catalyst and allowed the synthesis of either syn- or a...

miscellaneous_information

Rate and equilibrium constants for the reaction between N-aryl triazolium N-heterocyclic carbene (NHC) precatalysts and substituted benzaldehyde derivatives to form 3-(hydroxybenzyl)azolium adducts under both catalytic and stoichiometric conditions have been measured. Kinetic analysis and reaction profile fitting of both the forward and reverse rea...

miscellaneous_information

Rate and equilibrium constants for the reaction between N-aryl triazolium N-heterocyclic carbene (NHC) precatalysts and substituted benzaldehyde derivatives to form 3-(hydroxybenzyl)azolium adducts under both catalytic and stoichiometric conditions have been measured. Kinetic analysis and reaction profile fitting of both the forward and reverse rea...

The exploration and expansion of the scope of the isothiourea-mediated synthesis of dihydropyridinones is presented. The use of ketimines derived from alpha,beta-unsaturated gamma-ketoesters as the Michael acceptor in a Michael addition/lactamisation cascade gives access to a range of dihydropyridinones with high enantio-selectivity. The nature of...

Isothiourea HBTM-2.1 catalyses the Michael addition-lactonisation of 2-aryl and 2-alkenylacetic acids and α,β-unsaturated trichloromethyl ketones. Ring-opening of the resulting dihydropyranones and subsequent alcoholysis of the CCl3 ketone with an excess of methanol gives a range of diesters in high diastereo- and enantioselectivity (up to 95 : 5 d...

The synthesis of rigid symmetric polyradical model systems with inter-spin distances between 1.4 and 4 nm and their room temperature continuous wave (CW) EPR spectra are reported. Conditions for attachment of the spin-label via esterification have been optimized on the direct synthesis of polyradicals from commercially available polyphenols and the...

A stereodivergent asymmetric Lewis base catalyzed Michael addition/lactonization of enone acids into substituted dihydrobenzofuran and tetrahydrofuran derivatives is reported. Commercially available (S)-(−)-tetramisole hydrochloride gives products with high syn diastereoselectivity in excellent enantioselectivity (up to 99:1 d.r.syn/anti, 99 % eesy...

miscellaneous_information

N-Heterocyclic carbene (NHC)-catalyzed redox asymmetric hetero-Diels-Alder reactions of alpha-aroyloxyaldehydes with beta-trifluoromethyl enones generates synthetically useful dihydropyranones containing a stereogenic trifluoromethyl substituent in good yields (up to 81%) and excellent diastereoselectivity and enantioselectivity (up to >95:5 dr and...

Asymmetric α-amination through an N-heterocyclic carbene (NHC)-catalyzed redox reaction of α-aroyloxyaldehydes with N-aryl-N-aroyldiazenes to form α-hydrazino esters with high enantioselectivity (up to 99% ee) is reported. The hydrazide products are readily converted into enantioenriched N-aryl amino esters through samarium(II) iodide mediated N-N...

This protocol describes the synthesis of (S)-4-(4-hydroxybenzyl)-oxazolidin-2-one, its attachment to a Merrifield-Cl resin and its use for asymmetric synthesis. The chiral auxiliary is prepared in four steps from N-Boc-L-tyrosine on a multigram scale in high yield and attached to Merrifield-Cl resin via its phenolic group to afford a solid-supporte...

A substrate-depending diastereoselectivity is observed which provides predominantly the syn products from γ-aryl α-ketophosphonates of type (II) and (VII).

N-Heterocyclic carbene (NHC)-redox catalysed asymmetric hetero-Diels-Alder reactions of alpha-aroyloxyaldehydes with beta-trifluoromethyl enones generates synthetically useful dihydropyranones containing a stereogenic trifluoromethyl substituent in good yields (up to 81%) and excellent diastereo- and enantioselectivity (up to >95:5 dr and >99% ee)....

Chiral NHCs catalyse the asymmetric formal [2+2]-cycloaddition of alkylarylketenes with both electron deficient benzaldehydes and 2- and 4-pyridinecarboxaldehydes to generate stereodefined beta-lactones. In the benzaldehyde series, optimal product diastereo- and enantiocontrol is observed using 2-nitrobenzaldehyde (up to 93:7 dr (syn:anti) and 93%...

Acid chlorides can be activated using a simple iodide source to undergo nucleophilic attack from a variety of relatively weak nucleophiles. These include Friedel-Crafts acylation of N-methylpyrroles, N-acylation of sulfonamides, and acylation reactions of hindered phenol derivatives. The reaction is believed to proceed through a transient acid iodi...

[3153-26-2] C10H14O5V (MW 265.18) InChI = 1S/2C5H8O2.O.V/c2*1-4(6)3-5(2)7;;/h2*3,6H,1-2H3;;/q;;;+2/p-2/b2*4-3-;;InChIKey = JFHJZWAQYMGNBE-SUKNRPLKSA-L(precatalyst for oxidation of several functional groups in combination with alkyl hydroperoxides or oxygen;1 especially useful for the regio- and diastereoselective epoxidation of allylic alcohols,2 t...

Air-stable and crystalline N-acyl DBN tetraphenylborate salts have been shown to be effective O-acylating agents, reacting with both primary and secondary alcohols to give the corresponding esters in good yields. In the case of diols, the N-acyl DBN·BPh4 salts have been shown to acylate regioselectively the primary alcohol functionality in the pres...

Treatment of unsaturated amides of type (I), (IV), and (IX) with NMO/OsO4 leads to triols which spontaneously undergo cyclization to afford biologically important optically active hydroxy-γ-butyrolactones.

Dioctylaminesulfonamide-modified carbon nanoparticles are characterised and employed as high surface area substrate for (i) coenzyme Q10 and (ii) 1,2-dimyristoyl-sn-glycero-3-phosphocholine (or DMPC) - Q10 redox processes. The carbon nanoparticles provide a highly hydrophobic substrate with ca. 25 Fg-1 capacitance when bare. Q10 or DMPC-Q10 immobil...

Over the last ten years there has been a huge increase in development and applications of organocatalysis in which the catalyst acts as a nucleophile. Amidines and guanidines are often only thought of as strong organic bases however, a number of small molecules containing basic functional groups have been shown to act as efficient nucleophilic cata...

Air-stable and crystalline N-acyl DBN tetraphenylborate salts have been synthesized from 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and the corresponding acyl chloride in the presence of sodium tetraphenylborate. The salts have been shown to be effective N-acylating agents, reacting with primary amines, secondary amines, and sulfonamides to form the co...

The cyclopropane ring opening reaction is mediated by Hg(O-CO-CF3)2, leads after demetalation to chiral δ-lactones with multiple stereocenters.

A method of preparing enantiopure hydroxy-γ-butyrolactones containing multiple contiguous stereocenters in high yield with good diastereoselectivity has been developed. Osmium tetroxide mediated dihydroxylation of a range of β-alkenyl-β-hydroxy-N-acyloxazolidin-2-ones results in formation of triols that undergo spontaneous intramolecular 5-exo-trig...

An amphiphilic carbon nanofibre membrane electrode (ca. 50nm fibre diameter, 50–100μm membrane thickness) is employed as an active working electrode and separator between an aqueous electrolyte phase (with reference and counter electrode) and an immiscible organic acetonitrile phase (containing only the redox active material). Potential control is...

A versatile methodology for the asymmetric synthesis of chiral δ-lactones containing multiple contiguous stereocenters has been developed that relies on a series of Evans' aldol, hydroxyl-directed cyclopropanation, methanolysis, and Hg(II) mediated cyclopropane ring-opening reactions for stereocontrol.

2-Bromomethyl-9,10-anthraquinone is covalently bound to carbon nanoparticle surfaces (Emperor 2000, Cabot Corp., with sulphonamide groups, ca. 9 to 18 nm diameter) with a coverage of ca. 250 anthraquinone molecules per particle (ca. 180 Å2 per anthraquinone). The resulting hydrophobic carbon particles are dispersed in ethanol and coated onto glassy...

A practically simple three-component Strecker reaction for the asymmetric synthesis of enantiopure α-arylglycines has been developed. Addition of a range of aryl-aldehydes to a solution of sodium cyanide and (S)-1-(4-methoxyphenyl)ethylamine affords highly crystalline (S,S)-α-aminonitriles that are easily obtained in diastereomerically pure form. H...

A practically simple three-component Strecker reaction for the asymmetric synthesis of enantiopure alpha-arylglycines has been developed. Addition of a range of aryl-aldehydes to a solution of sodium cyanide and (S)-1-(4-methoxyphenyl)ethylamine affords highly crystalline (S,S)-alpha-aminonitriles that are easily obtained in diastereomerically pure...

1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) has been shown to be an effective catalyst for the regioselective Friedel-Crafts C-acylation of pyrroles and indoles in high yields. A detailed mechanistic study implies that DBN is acting as a nucleophilic organocatalyst, with the X-ray crystal structure of a key N-acyl-amidine intermediate having been determ...

The surface functionalities of commercial sulfonate-modified carbon nanoparticles (ca. 9-18 nm diameter, Emperor 2000) have been converted from negatively charged to positively charged via sulfonylchloride formation followed by reaction with amines to give suphonamides. With ethylenediamine, the resulting positively charged carbon nanoparticles exh...

The use of [Cp*IrI2]2 as an efficient catalyst for the alkylation of amines by alcohols in either water or ionic liquid is described. Primary amines are converted into secondary amines, and secondary amines into tertiary amines in the absence of base, and the chemistry has been applied to the synthesis of the analgesic fentanyl. The conversion of p...

ChemInform 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.

Alkyne-1,4-diols are readily available substrates which are isomerised to 1,4-diketones using Ru(PPh3)3(CO)H2/xantphos as a catalyst. In situ cyclisation into furans, pyrroles and pyridazines has been achieved under suitable conditions.

A carbohydrate sensing "click-fluor" is reported which displays a nontypical binding preference with sample saccharides. That a fluorescent sensor is generated as a result of triazole formation (click reaction), rather than simply bringing the sensor and reporter units together via a triazole linkage, and the potential applicability of the wide ran...

Nimm zwei: Die intermolekulare doppelte [2+2]-Cyclodimerisierung von Vinylidenbisalkinen liefert einen luftstabilen Organometallkomplex mit einem ungewöhnlichen Ligandenmotiv (siehe Schema). Der zentrale sechsgliedrige Ring enthält nur sp2-hybridisierte Kohlenstoffatome und zwei exocyclische Doppelbindungen und ist ein stabiles desaromatisiertes An...

Cotton is an excellent cellulose-based absorbent mainly due to amorphous cellulose regions in the nanocrystalline (cellulose-I) natural fiber structure. It is shown here for the case of a woven cotton textile with ca. 20 μm fiber diameter and ca. 270 μm thickness that cation and anion absorption and diffusion processes occur within cotton fibers. A...

Voltammetric measurements at the surface of cotton fabric were conducted after impregnating the surface of the textile with graphite flakes. The resulting conducting surface contact was connected to a conventional basal plane pyrolytic graphite substrate electrode and employed both in stagnant solution and in rotating disc voltammetry mode. Diffusi...