M. Belén Cid

Nitrophenylacetonitriles as versatile nucleophiles in enantioselective organocatalytic conjugate additions.

Arylacetonitriles are able to participate in organocatalytic Michael additions to alpha,beta-unsaturated aldehydes by incorporating a nitro group at the phenyl ring, which acts as a temporary activating group in a remote position and allows further transformations. The sequential protocol Michael addition/NaBH(4) reduction/lactonization allows the synthesis of diastereomerically pure disubstituted lactones in high yield and optical purity.

An Efficient Method for the Synthesis of Nitropiperidones

A three step efficient strategy for the synthesis of substituted 5-nitropiperidones in high de, employing Michael addition of N-p-tolylsulfinyl beta-nitroamines to alpha,beta-unsaturated esters, hydrolysis of the sulfinyl group, and cyclization of the resulting free amines, has been developed. A very simple experimental procedure involving mild conditions and only one chromatographic purification are the main features of the process.

Diels-Alder reactions of [(S)R]-(1E,3E)-1-p-tolylsulfinyl-1,3-pentadiene: the unexpected evolution of maleic anhydride adducts

Abstract The Diels-Alder adducts resulting in the reaction of enantiomerically pure [(S)R]-(1E,3E)-1-p-tolylsulfinyl-1,3-pentadiene with maleic anhydride evolved stereoselectively in situ through several intramolecular tandem reactions, involving [2,3]-sigmatropic sulfoxide-sulfenate rearrangement, acylation of the sulfinyl oxygen, and elimination of the sulfur function through a SN2′ process yielding lactones 3 and 4.

Synthesis and Diels-Alder reactions of homochiral 2-sulfinylmaleates with cyclopentadiene

Abstract Enantiomerically pure 2-p-tolylsulfinylmaleates 1, 2 and 3 have been readily prepared by Knoevenagel reaction between (S)-menthyl p-toluenesulfinate and glyoxylic acid. Their asymmetric Diels-Alder reactions with cyclopentadiene have been studied under a wide range of uncatalyzed and catalyzed conditions and the stereochemical results have been explained by assuming a steric control approach, in term of S-cis or S-trans favoured conformations. Uncatalyzed Diels-Alder reactions of 1 and some Lewis acid catalyzed Diels-Alder reactions of 2 show high facial and endo selectivities. The facial selectivity of dienophile 2 highly depends on the Lewis acid, whereas reactivity of 1 and 3 is very sensitive to the solvent. These sulfinylmaleates 1, 2 and 3 act as synthetic equivalents of chiral acetylenedicarboxylates in Diels-Alder reactions after basic elimination of the sulfinylic moiety in the resulting adducts.

Organocatalytic Michael addition/intramolecular Julia-Kocienski olefination for the preparation of nitrocyclohexenes.

An asymmetric organocatalytic [3 + 3] annulation strategy based on a Michael addition/intramolecular Julia-Kocienski olefination sequence has been developed for the synthesis of 4-substituted-5-nitrocyclohex-1-ene compounds. The strategy is an alternative to the direct reluctant enantioselective Diels-Alder approach. The potential of the methodology has been demonstrated with a concise enantioselective formal synthesis of trandolapril.

DIELS-ALDER REACTIONS OF (S)R-(1E,3E)-1-P -TOLYLSULFINYL-1,3-PENTADIENE WITH MONOSUBSTITUTED ETHYLENES

Abstract Diels-Alder reactions of [(S)R]-(1E,3E)-1-p-tolylsulfinyl-1,3-pentadiene with 1-pyrrolidinyl-1-cyclohexene and methyl acrylate evidenced: i) low reactivity of the diene regardless of the electronic character of the dienophile (high pressures were always required); ii) a complete regio- and endo-selectivity (both controlled by the sulfoxide), but a low π-facial diastereoselectivity in the cycloaddition with enamine; iii) diastereoselectivity (facial and endo exo ) for the reaction with methyl acrylate is dependent on the regiochemistry (mainly controlled by the methyl substituent).

Diels-alder reactions of 1-sulfinyldienes with an endocyclic double bond: The unexpected evolution of the n-methylmaleimide adducts.

Abstract ( R )-(1 E ,3 E )-2-Cyclohexenyl-1-vinyl- p -tolylsulfoxide 1a and ( R )-(1 E ,3 E )-N-methyl-3-[2-( p -tolylsulfinyl) vinyl]-1H-in 1b reacted with N-methylmaleimide to give Diels-Alder adducts whose in situ evolution through a tandem sulfoxide-sulfenate rearrangement/dehydration/[4+2]-cycloaddition sequence afforded the all- cis substituted bicyclo [2,2,2] octene 7 in a highly stereoselective manner.

An organocatalytic approach to enantiomerically enriched α-arylcyclohexenones and cyclohexanones

The presence of a p-nitrophenyl group converts acetone into an excellent and versatile nucleophile in organocatalytic processes, able to react with α,β-unsaturated aldehydes affording β-substituted α-arylcyclohexenones via a Michael reaction/aldol reaction/dehydration sequence, which occurs in good yields, ee up to 96% and complete diastereoselectivity. The resulting compounds are excellent synthons for the diastereoselective preparation of a variety of synthetically useful polysubstituted cyclohexanones and derivatives.

A horner-wadsworth-emmons approach to [(S)R]-4-substituted 1-p-tolylsulfinyl-1,3-dienes☆

Abstract [(S) R ,1 E ,3 E ]-4- p -Tolylsulfinyl-1-X-1,3-butadienes 1 (X = CO 2 Me, CN, PO(OEt) 2 , SO 2 Ph, SEt) are synthesized from a common starting material, [(S) R ]-3- p -tolylsulfinyl-2-propenal 2 , through a Hormer-Wadsworth-Emmons reaction with the phosphonate (XCH 2 PO(OEt) 2 ). The synthesis of 2 is also described.

Unexpected reactivity of graphene oxide with DBU and DMF

An unusual reaction between GO, DBU and DMF, that typically uses base and solvent, has been thoroughly analyzed providing valuable basic knowledge about the reactivity of GO, which is essential to control functionalization and therefore the properties of graphene derivatives. A combination of characterization techniques, experiments and theoretical calculations allowed us to propose a structure for the materials and a plausible mechanism. The catalytic activity of the new basic materials was also analyzed.