Alan H. McNeill

The scope and limitations of deuteration mediated by Crabtree's catalyst

Abstract Exchange of protons for deuterons mediated by Crabtrees catalyst, 1, is directed efficiently by a functional group containing an sp2-hybridised nitrogen or oxygen atom; more electron-rich substrates are, in general, deuterated more efficiently. The electronic effects of substituents in the arene ring are critical only where the directing group is poor, in which case exchange is generally promoted by electron donating substituents, but the exchange is impeded by bulky meta-substituents.

1,5-Asymmetric induction in reactions betweenδ-alkoxyallylstannanes and aldehydes induced by tin (IV) chloride

Treatment of (S)-4-benzyloxypent-(2E)-2-enyl(tributyl)stannane (3) with tin (IV) chloride at −78 °C, followed by the addition of an aldehyde, gives 1,5-diol derivatives (6) with excellent 1,5-diastereoselectivity.

Conditions for deuterium exchange mediated by iridium complexes formed in situ

Abstract A series of iridium-based complexes formed in situ, containing pyridine, phosphines, triphenylarsine, triphenylstibine, and triphenylamine as ligands, has been screened for ability to mediate ortho-exchange of hydrogen in a series of model substrates. Improved incorporation into a number of substrate classes has been achieved. The electronic properties and number of ligands at the metal centre are instrumental in determining which catalysts are best suited to exchange in any given substrate.

Deuterium exchange mediated by an iridium–phosphine complex formed in situ

Bis(triorganophosphine)(cyclooctadiene)iridium(I) tetrafluoroborates, 2, are readily generated in situ and utilised for the exchange of deuterium into a variety of aromatic substrates. The efficiencies of deuterium exchange using 2 formed in this way are comparable to those observed in exchange processes where the isolated pre-catalysts were used.

1,5-Asymmetric induction in reactions of δ-alkoxyallylstannanes: stereoselective reactions with chiral aldehydes

Abstract Transmetallation of (4 S ,2 E )-4-phenylmethoxypent-2-enyl(tributyl)stannane 1 using tin(IV)chloride generates a reagent which shows excellent 1 5-stereoselectivity in reactions with aldehydes: with chiral aldehydes, the stereochemical preference of the reagent dominates the course of the reaction.

The improved synthesis of β-D-glucuronides using TEMPO and t-butyl hypochlorite

Abstract TEMPO/t-BuOCl is used to oxidise β-D-glucosides to β-D-glucuronides in high yield as a pivotal step in the preparation of labelled glucuronides from labelled glucose samples.

Preparation of indole-2-carboxamides by palladium-catalysed carbonylation

Abstract Palladium-mediated carbonylation of a 2-iodoindole in the presence of an amine provides an efficient method for the preparation of indole-2-carboxamides. The process is clean and rapid, and appears to be general where the amine component is sufficiently non-volatile.

Stereoselective synthesis of aliphatic 1,5,9,13-polyols using (δ-alkoxyallyl)stannanes

Abstract Treatment of aliphatic aldehydes with the allyltin trichloride generated from the 4-benzyloxyocta-2,7-dienylstannane 18 and tin(IV)chloride provides stereoselective access to polyhydroxylated compounds with the hydroxyl groups at positions 1,5,9,13− etc. along the aliphatic chain.