Aurelia Pastor

6π-electrocyclization of azahexa-1,3,5-trienes: a new entry to a regiospecific synthesis of 3-aryl(heteroaryl)pyridines

Abstract Aza Wittig reaction of iminophosphoranes derived from ethyl α-azido-β-aryl(pyrazolyl)propenoates with α,β-unsaturated aldehydes leads to aldimines which by heating undergo electrocyclic ring-closure through the 3-azahexa-1,3,5-triene moiety to give 3-aryl(pyrazolyl)pyridines in a completely regiospecific fashion. However, iminophosphoranes derived from ethyl α-azido-β-furyl(thienyl)propenoates furnish a mixture (1.2:1 ratio) of the corresponding furo- or thieno-pyridine(2-azahexa-1,3,5-triene electrocyclization product) and 3-furyl(thienyl)pyridine(3-azahexa-1,3,5-triene electrocyclization product).

Small-molecule recognition for controlling molecular motion in hydrogen-bond-assembled rotaxanes.

Di(acylamino)pyridines successfully template the formation of hydrogen-bonded rotaxanes through five-component clipping reactions. A solid-state study showed the participation of the pyridine nitrogen atom in the stabilization of the mechanical bond between the thread and the benzylic amide macrocycle. The addition of external complementary binders to a series of interlocked bis(2,6-di(acylamino)pyridines) promoted restraint of the back and forward ring motion. The original translation can be restored through a competitive recognition event by the addition of a preorganized bis(di(acylamino)pyridine) that forms stronger ADA-DAD complexes with the external binders.

An efficient preparation of novel ferrocene derivatives via aza Wittig reaction and X-ray structure of bis(β-ferrocenylvinyl)carbodiimide

Novel ferrocene derivatives such as β-ferrocenylvinylheterocumulenes and ferrocene-containing imidazole rings have been easily prepared from β-ferrocenylvinyliminophosphorane 3 by Aza Wittig reactions.

Highly diastereoselective self-assembly of chiral tris(m-ureidobenzyl)amino capsules

The self-assembly of chiral tris(m-ureidobenzyl)amines to give dimeric capsules is a highly diastereoselective process in solution, while in the solid state, the formation of the corresponding capsules is not only diastereoselective but also regioselective.

Electrocyclization of 3-azahexa-1,3,5-trienes: A convenient iminophosphorane-mediated preparation of 4-arylpyridines

Aza Wittig reaction of iminophosphoranes 1, derived from α-azido- α,β-unsaturated esters and β-arylpropenals 2 leads to 4-arylpyridines in moderate to good yields.

Vinyliminophosphorane-mediated preparation of 2-arylquinoline and 4-aryl-1-azaanthraquinone derivatives. X-Ray crystal structure of 1,2-dihydro-3H-indazolo[2,3-a]quinolin-4-one

Abstract The reaction of the iminophosphorane derived from 3-azidocyclohexen-2-enone with substituted cinnamyl aldehydes affords 2-aryl-tetrahydroquinoline derivatives, which are easily converted into 2-arylquinolines. By contrast, iminophosphorane derived from 2-azidocyclohex-2-enone reacts only with α,β-unsaturated aldehydes without substituent at β-position to give 5,6-dihydro-8(7H)quinolinones. The iminophosphorane derived from 2-azido-1,4-naphthoquinone reacts with substituted cinnamyl aldehydes providing directly 4-aryl-1-azaanthraquinones. The crystal and molecular structure of 1,2-dihydro-3H-indazolo[2,3-a]quinolin-4-one has been solved by X-Ray analysis.

Polar Hetero-Diels−Alder Reactions of 4-Alkenylthiazoles with 1,2,4-Triazoline-3,5-diones: An Experimental and Computational Study

The hetero-Diels-Alder reactions of 4-alkenylthiazoles with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) lead to new heteropolycyclic systems in excellent yields and high levels of stereocontrol through an exclusively suprafacial approach. 4-Alkenylthiazoles with a stereogenic center placed at the alkenylic substituent react with PTAD giving the corresponding chiral cycloadducts in moderate diastereomeric excesses. The stereochemical course is dominated by the steric interactions at the two diastereomeric transition states. A computational study of these processes with structurally simpler reagents has been carried out. A concerted pathway via a highly asynchronous transition state is preferred for 2-unsubstituted 4-vinyl and 4-styrylthiazoles. However, two alternative and equally likely pathways, concerted and stepwise, have been found to be followed by 2-methyl- or 2-phenyl-substituted 4-styrylthiazoles. The concerted pathway features a highly asynchronous transition state. For the stepwise pathway, the rate-determining step is the first one, as the energy barrier for the second step is virtually nonexistent.

Dimerization of tris(o-ureidobenzyl)amines: a novel class of aggregates

Dimeric aggregates are formed by the assembly of two tripodal moieties which are held together, both in solution and in the solid state, by a belt of 6 hydrogen-bonded urea functions.

Synthesis and Molecular Structure of β‐Phosphinoyl Carboxamides: An Unexpected Case of Chiral Discrimination of Hydrogen‐Bonded Dimers in the Solid State

A series of N,P,P-trisubstituted aminophosphanes react with diphenylcyclopropenone to afford an easily separable mixture of two diastereomeric alpha,beta-diphenyl-beta-phosphinoyl carboxamides in good yields. X-ray crystal structures reveal that these compounds associate into dimers, formed from two enantiomeric units linked by two bifurcated hydrogen bonds, whereby the oxygen atom of the phosphoryl group acts as a dual acceptor for the vicinal NH and CH of a carbonyl group of a neighbouring molecule. Studies on the interconversion between diastereomeric phosphinoyl carboxamides in basic solution show that the thermodynamically most stable isomer depends on the nature of the substituent at the nitrogen atom. Simple computational calculations explain this phenomenon.

SYNTHETIC APPLICATIONS OF VINYLIMINOPHOSPHORANES BASED ON THE REACTIVITY OF THE VINYL SIDE CHAIN : PREPARATION OF DIHYDROPYRIDINES

Abstract New reactions of vinyliminophosphoranes with aldehydes involving an initial nuclcophilic attack of the β-carbon atom of the vinyl side chain on the carbonylic carbon atom is reported. The resulting bctaines undergo either intra- or intermolecular cyclization to give pyridines or dihydropyridines.