Palladium(II)-catalyzed cyclization of heterocyclic ketene aminals with (E)-ethyl 2,3-diiodoacrylates: selective synthesis of bicyclic pyrroles and bicyclic pyridones

A concise and efficient synthesis of novel bicyclic pyrroles has been achieved by PdCl₂-catalyzed cyclic condensation of six-membered heterocyclic ketene aminals (HKAs) or seven-membered HKAs with ethyl 2,3-diiodoacrylate and diethyl 2,3-diiodofumarate in the presence of Cs₂CO₃, respectively. A series of novel bicyclic pyridones have also been obtained via five-membered HKAs with diethyl 2,3-diiodofumarate under the optimized conditions in moderate yields. These reactions are the first application of a transition metal to catalyze the building blocks HKAs to form the bicyclic pyrrole library via condensation reaction.     

Synthesis of O-Glycosides of Heteroatom Aroyl-Substituted Heterocyclic Ketene Aminals

Asweknow,carbohydratesplayanimportantroleinnature,especiaIlyasrecogniti0ndeterminantinhost-pathogeninteractionsorinceIl-cellinteractions.Theref0re,stereo-controlledglucosylationhasbecomeone0ftheimportantt0picsinorganicsynthesis]'2.HeterocyclicketeneaminaIsareimportantintermediatesforthesynthesis0fawidevarietyofnewheterocyclesandfusedheterocycles,someofwhichhavehighbiologicalactivity'.IthasbeenrepoFtedthatbenzoyl-substitutedheterocyclicketeneaminalscanreactwith2usingmercuriccyanideascatalystt…     

Total Synthesis of (+)‐Dibromophakellin and (+)‐Dibromophakellstatin

A new method for the preparation of quaternary chiral aminals has been developed that employs an enamide‐type Overman rearrangement process. This methodology was applied to enantioselective total syntheses of (+)‐dibromophakellin and (+)‐dibromophakellstatin.     

An efficient one-pot route to symmetrically and unsymmetrically substituted 1,4,7-triazacyclononanes also results in the isolation of a stable macrocyclic aminal

A one-pot methodology has been developed for the direct synthesis of symmetrically and unsymmetrically N-substituted derivatives of 1,4,7-triazacyclononane. In the course of these studies the unexpected eight-membered cyclic aminal 7 has been isolated via an acid-catalysed rearrangement of enamine 5.     

Effect of pH on the reaction outcome between tetraacetyl hexaazaisowurtzitane and aldehydes

2,6,8,12-Tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane was subjected to N-aminomethylation under various conditions, which afforded new derivatives of aminal nature. The highest yields were achieved when the reactions were carried out in a weak-alkali medium.     

New cage-fused polyaza polycyclic systems based on thioglycolurils and alkanediamines

1. Download : Download high-res image (91KB)
2. Download : Download full-size image

     

Cascade reaction synthesis of multisubstituted bicyclic pyridone derivatives

An efficient synthesis of novel bicyclic pyridone derivatives via cascade reaction of heterocyclic ketene aminals (HKAs) and 4-arylmethylene-2-phenyloxazol-5(4H)-ones in the presence of acetic acid has been established. Significantly, the protocol affords a straightforward approach to the construction of multisubstituted bicyclic pyridones in which one C–O bond was cleaved and new C–C and C–N bonds were formed in one pot under mild conditions.     

Three-component domino reaction synthesis of highly functionalized bicyclic pyrrole derivatives

An efficient one-pot synthesis of highly functionalized bicyclic pyrrole derivatives by a three-component domino reaction of heterocyclic ketene aminals (HKAs), arylglyoxal monohydrate, and indoles in ethanol medium catalyzed by acetic acid is described. In this procedure, three sigma bonds were formed simultaneously. The present synthesis features excellent regio-selectivity, easy purification as well as simple starting materials.     

New amidines from intramolecular cyclization in triflic acid of nitroketene aminals with a tethered phenyl ring

Nitroketene aminals with a tethered phenyl group underwent an intramolecular cyclization in trifluoromethanesulfonic acid to afford the corresponding N-(3-ethyl-hydrohydroxyiminobenzocyclo-alkenylidene)methylamine trifluoromethanesulfonate. The yields were fair to good excepted for the starting compound 1-[N-ethyl-N-(2-phenylethyl)amino]-1-methylamino-2-nitroethene.     

Dehydration Rearrangements of Derivatives of Methylenedihydrobenzofuran - a New Path to Substituted Benzofurans

When heated with acidic agents derivatives of 3-amino-2-(hydroxydialkylmethyl)methylene-2,3-dihydrobenzofuran undergo rapid dehydration and rearrangement to substituted 2-alkenyl-3-aminobenzofurans.