Allylic alkylation versus Michael induced ring closure: chelated enolates as versatile nucleophiles.

Allylic carbonates 8 bearing an electron-withdrawing ester functionality can act as substrates for palladium-catalyzed allylic alkylations or as Michael acceptors with the option to undergo subsequent ring closure. Chelated amino acid ester enolates 1' are versatile nucleophiles for both reactions giving high yields and selectivites.

Molybdenum-catalyzed stannylations as key steps in heterocyclic synthesis.

THF/carbonyl complexes of molybdenum and tungsten are suitable precursors for the synthesis of the corresponding monoisonitrile carbonyl complexes. Whereas complexes with electron-rich isonitriles are suitable for regioselective hydrostannations, complexes with electron-poor isonitriles are efficient catalysts for distannations, without reduction of aromatic halides. This allows for the synthesis of halogenated distannylated allyl ethers, which can be subjected to intramoleculare Stille couplings giving rise to heterocycles, which can be further modified at the remaining stannyl group.

Efficient stereoselective syntheses of cyclic amino acids via Michael-induced ring-closing reactions.

[reaction: see text] Zn-chelated glycine ester enolates are highly efficient nucleophiles for the synthesis of trans-methoxycarbonylcyclopropyl- and cyclobutylglycines by domino sequences of Michael additions and subsequent ring closures. They react to give the anti isomers with high yields and excellent diastereoselectivities.