Christopher J. Urch

Palladium catalysed ter- and tetra-molecular queuing processes. One-pot routes to 3-spiro-2-oxindoles and 3-spiro-2(3H)-benzofuranones

Abstract The palladium catalysed reactions of 2-halophenols and -anilines with vinyl halides or triflates and CO(1atm) generates 3-spiro-2-oxindoles and 3-spiro-2(3H)-benzofuranones. Analogous tetramolecular reactions employing norbornenyl triflate and organo-tin(IV) or -boron(III) reagents allow additional functionality to be incorporated regio- and stereo-specifically.

Stereospecific cyclopropane synthesis from γ-stannyl alcohols

Abstract γ-Stannyl tertiary alcohols and γ-stannyl benzyl alcohols form cyclopropanes stereospecifically on treatment with acid, with inversion of configuration at both carbon atoms.

ELECTROCHEMICALLY DRIVEN CATALYTIC PD(0)/CR(II) MEDIATED COUPLING OF ORGANIC HALIDES WITH ALDEHYDES. THE NOZAKI-HIYAMA-KISHI REACTION

Abstract An electrochemically driven, catalytic, Pd(0)/Cr(II) mediated coupling of organic halides with aldehydes is described. The reaction proceedes under mild conditions and the influence of reaction conditions and the mechanism are briefly discussed.

Conjugate addition of the phenyldimethylsilyl group to αβ-unsaturated carbonyl compounds using a silylzincate in place of the silylcuprate

Lithium phenyldimethylsilyl(dialkyl)zincates add to a number of αβ-unsaturated carbonyl compounds to give, in most cases, higher yields of the conjugate addition product than we had achieved with the corresponding silylcuprate.

Studies towards the synthesis of lophotoxin and pukalide: Synthesis of the 14-membered macrocyclic core and some acyclic structural analogues

The 14-membered macrocycle 3, an advanced intermediate in a synthetic approach to lophotoxin, was prepared from stannane 20 using an intramolecular Stille coupling. The acyclic structural analogues 6 and 7 were obtained by analogous intermolecular coupling reactions.

Regiochemical Directing Effects in Palladium Catalyzed Alkylations with Polyene Electrophilic Partners

Abstract Unusual regioselectivity in alkylations arise as a result of the dynamic behavior of trihapto pentadienyl metal complexes, a phenomenon previously studied from a theoretical point of view.

STEREOSELECTIVE STILLE COUPLING REACTIONS OF 1,1-BIS(TRIALKYLSTANNYL)ETHENES

Abstract Stille coupling of 1,1-bis(tri-n-butylstannyl)ethenes proceeds in a stereoselective manner to afford the E-vinylstannanes. Repetition of this sequence affords a new route to tri-substituted alkenes. Intramolecular Stille coupling of a suitable vinyl bromide affords a pyranyl-derived vinylstannane. In certain cases, with bulky electrophiles, butyl migration rather than that of the sp2 - hybridised centre is observed. A working model is put forward in order to rationalise these results.

On the cine substitution of 1,1-bis(tri-n-butylstannyl)ethenes in an intramolecular Stille reaction

Abstract An attempted intramolecular Stille coupling of a bis-stannylethene proceeds not by ipso-substitution (7-endo-cyclisation) but via a cine substitution pathway (6-exo-cyclisation). Deuterium labelling studies and blank reactions are in consonance with a palladium carbene mechanism originally put forward by Busacca to explain the cine substitution reactions of styrylstannanes.

1,1-Bis(trialkylstannyl)ethenes: Further investigations into their reactivity

Ipso halodestannylation of 1,1-bis(tributylstannyl)ethenes with one equivalent of halogen leads to a variety of 1-halovinylstannanes. In certain cases, these reactions exhibit high levels of stereoselectivity. A plausible mechanistic pathway is advanced in order to explain the stereochemical outcome of these reactions. Addition of two equivalents of halogen affords the corresponding 1,1-bis-haloalkenes complementing existing methodology (e.g. Corey-Fuchs reaction) for the preparation of these useful synthetic intermediates.

Novel synthesis of oxindoles from carbamoyl chlorides via palladium catalysed cyclisation–anion capture

The synthesis of 3,3-disubstituted and 3-methyleneoxindoles by npalladium(0) catalysed cyclisation of carbamoyl chlorides onto nproximate alkene or alkyne groups has been achieved in good yields.