Andreas Stolle

The virtue of methylenecyclopropane terminators in intramolecular Pauson-Khand reactions

Abstract 6-Cyclopropylidene-1-hexynes like 2 , e. g. prepared via palladium(0)-catalyzed substitution of 1-ethenyl cyclopropyl sulfonates 1 , undergo an intramolecular Pauson-Khand reaction both efficiently and regioselectively.

Enantioselective construction of spiro{cyclopropane-14′-bicyclo[3.3.0]oct-1-en-3-ones}

Abstract Intramolecular Pauson-Khand reactions of 1,6-enynes 3a–c with a methylenecyclopropane terminator and a chiral acetal moiety adjacent to the triple bond gave spiro{cyclopropane-1,4′-bicyclo[3.3.0]oct-1-en-3-ones} 5a–c in good yields with a diastereoselectivity of up to 6.4:1. The major diastereomer of 5b was converted to enantiomerically pure bicyclo[3.3.0]octane-3,8-dione 8 , which showed a negative peak at 287 nm in the CD curve, consistent with an assumed (5 R ) configuration.

Regioselective palladium (O) catalyzed azidation and amination of 1-alkenylcyclpropyl esters: a new route to 2,3-methanoamino acids.

Abstract Palladium (O) catalyzed azidation of 1-alkenylcyclopropyl esters provides regioselectively 1-azido-1-alkenyl cyclopropanes, convenient precursors of 2,3-methanoamino acids. On the other hand, amination occurred exclusively on the less substituted allylic end, providing strained 2-cyclopropylideneethylamine derivatives.

Regioselective palladium(0) catalyzed reduction of 1-alkenylcyclopropyl esters as equivalent of the wittig reaction §

Abstract Palladium(0) catalyzed reduction of 1-(1-alkenyl)- and 1-(1-cycloalkenyl)cyclopropyl esters provides an useful alternative to the Wittig reactions of cyclopropylidenetriphenylphosphorane or of cyclopropanone hemiacetals and an easy route to strained methylenecyclopropane derivatives.

Palladium(0) catalyzed substitution reactions of cyclopropyl group containing allylic esters

Abstract Complete regioselectivity is observed in palladium(0) catalyzed allylic substitution reactions of 1-vinylcyclopropyl 3 and cyclopropylldeneethyl esters 6 with a series of soft carbon nucleophiles to give γ-cyclopropylidene-1,3-dicarbonyl and 1-carbonyl-2-sulfonyl compounds. Highly functionalized mathylenecyclopropanes are thus obtained in good to excellent yields from easily accessible 1-vinylcyclopropyl tosylates 3d .