Intramolecular amidocyclopropanation reactions using diethoxymethyl-functionalised lactams as organozinc carbenoid precursors

Intramolecular amidocyclopropanation reactions of diethoxymethyl-lactams containing a pendant alkene were examined using zinc/TMSCI. With a range of 4-6-membered lactams, bicyclic amidocyclopropanes were obtained with very high diastereoselectivity with a preference for the formation of the More hindered endo-cyclopropane. (C) 2009 Elsevier Ltd. All rights reserved

Isocyanide based multicomponent reactions of oxazolidines and related systems

N-Alkyloxazolidines react in a multicomponent reaction with carboxylic acids and isocyanides to give N-acyloxyethylamino acid amides. The previously reported reaction conditions were improved using a design of experiments approach (DoE). Under the optimised conditions, good yields of the N-acyloxyethylamino acid amide products are obtained both via a three- or four-component approach from N-alkylethanolamines, aldehydes/ketones, isocyanides and carboxylic acids. The reaction of oxazolidines without a nitrogen substituent was found to give either the expected Ugi products or the N-acyloxyethylamino acid amides depending on the choice of reaction conditions. Optimised reaction conditions were also developed for the ring-expansion of oxazolidines to morpholin-2-ones via reaction with an isocyanide followed by hydrolysis. The mechanistic pathway of the multicomponent reaction was briefly investigated using an O-18 labelling experiment. The carboxylic acid component can be replaced by a range of other acidic nucleophiles including thiobenzoic acid, thiophenol or 5-phenyltetrazole, which are incorporated via an alternative pathway. These latter reactions can also be applied to 2-aminotetrahydrofurans, 2-aminotetrahydropyrans or 4-hydroxybut-2-one, further extending the structural diversity of the multicomponent reaction products. (C) 2010 Elsevier Ltd. All rights reserved

Functionalisation of terpenoids at C-4 via organopalladium dimers: cyclopropane formation during oxidation of homoallylic sigma-organopalladium intermediates with lead tetraacetate

The synthesis of new potential adjuvant saponin aglycons was investigated by selective palladium mediated C-H functionalisation of appropriately functionalised derivatives of lanosterol, cholesterol, and friedelin. The desired equatorial aldehyde functionality was successfully introduced into the lanosterol skeleton as expected. Cyclopalladation of a cholesterol derivative proceeded as expected, but during oxidation of the organopalladium intermediate, participation of the adjacent alkene functionality led to stereoselective formation of a cyclopropane and introduction of an acetate group into the steroid backbone at C-6. Further investigation of this unusual cyclopropane formation on a model decalin system confirmed the result, but C-H activation on a related open chain system was prevented by complexation of the alkene functionality to the palladium. (c) 2007 Elsevier Ltd. All rights reserved

Noncovalent Interactions of pi Systems with Sulfur: The Atomic Chameleon of Molecular Recognition

The relative strength of noncovalent interactions between a thioether sulfur atom and various π systems in designed top pan molecular balances was determined by NMR spectroscopy. Compared to its oxygen counterpart, the sulfur atom displays a remarkable ability to interact with almost equal facility over the entire range of π systems studied, with the simple alkene emerging as the most powerful partner. With the exception of the O⋅⋅⋅heteroarene interaction, all noncovalent interactions of sulfur with π systems are favoured over oxygen

ChemInform Abstract: Intramolecular Amidocyclopropanation Reactions Using Diethoxymethyl-Functionalized Lactams as Organozinc Carbenoid Precursors.

Intramolecular amidocyclopropanation reactions of diethoxymethyl-lactams containing a pendant alkene were examined using zinc/TMSCI. With a range of 4-6-membered lactams, bicyclic amidocyclopropanes were obtained with very high diastereoselectivity with a preference for the formation of the More hindered endo-cyclopropane. (C) 2009 Elsevier Ltd. All rights reserved