ABSTRACT
The synthesis of various heterocycles and carbocycles (tetrahydrofurans, pyrrolidines, cyclopentanes) has been achieved by using new and efficient ionic addition/cyclization sequences. Nitroolefins play an important role in the Michael addition induced ring-closing reactions (MIRC) reported in the present article, with various substituted alcohols, amines, Grignard reactants, or malonate derivatives acting as the nucleophile partner. The optimized cascade reactions were high yielding in most cases and highly stereoselective, creating up to three stereogenic centers starting from achiral substrates.
Subject(s)
Alkenes/chemistry , Cyclopentanes/chemical synthesis , Cyclopropanes/chemical synthesis , Furans/chemical synthesis , Heterocyclic Compounds/chemical synthesis , Cyclization , Cyclopentanes/chemistry , Cyclopropanes/chemistry , Furans/chemistry , Heterocyclic Compounds/chemistry , Molecular Structure , StereoisomerismABSTRACT
A new one-pot domino reaction for a general entry to functionalised bridged bicyclo[n.2.1] ring systems from alpha, alpha'-diactivated cyclic ketones and trans-1,4-dihalides is described. The sequence combines a base promoted C-O cycloalkylation reaction leading to fused polycyclic enol ethers and their in situ palladium-catalysed isomerisation.
Subject(s)
Bridged Bicyclo Compounds/chemistry , Furans/chemistry , Palladium/chemistry , Catalysis , Isomerism , Substrate SpecificityABSTRACT
[reaction: see text] Nitronic acids undergo an intramolecular 1,3-dipolar cycloaddition to unactivated double bonds, and the resulting isoxazolidines spontaneously evolve by an unprecedented in situ oxidative ring cleavage. The extension of this transformation to silyl nitronates results in a general diastereoselective construction of hydroxymethyl nitro functionalized tetrahydro-furans and -pyrrolidine having up to four consecutive stereogenic centers.