Synthesis of Dispirocyclopentyl‐3,3′‐bisoxindoles via Domino Cycloaddition Reactions of 4‐Dimethylaminopyridinium Bromides with 3‐Phenacylideneoxindoles

The base mediated cycloaddition reactions of 4‐dimethylamino‐1‐phenacylpyridinium bromides with two molecular 3‐phenacylideneoxindoles in methylene dichloride afforded functionalized dispirocyclopentyl‐3,3′‐bisoxindoles in good yields and with high diastereoselectivity. The similar cycloaddition reactions of 1‐(N,N‐dialkylcarbamoylmethyl) and 1‐cyanomethyl 4‐dimethylamino‐pyridinium bromide in refluxing ethanol in the presence of triethylamine also resulted in dispirocyclopentyl‐3,3′‐bisoxindoles with high diastereoselectivity. The stereochemistry of dispirocyclopentyl‐3,3′‐bisoxindoles was elucidated on the basis of ¹H NMR data and single crystal structures.     

trans-4-Hydroxy-l-proline: a novel starting material for N-alkylpyrroles synthesis

The reaction of aldehydes with trans-4-hydroxy-l-proline was studied for the first time, resulting in the formation of N-alkylpyrroles in good to excellent yields, via decarboxylation followed by redox isomerization under neutral conditions. The neutral conditions allow access to efficient synthesis of N-alkyl pyrroles with high functional group tolerance.     

Structural, theoretical and multinuclear NMR study of mercury(II) complexes with a new ambidentate phosphorus ylide

The reaction of the new ambidentate ylide, Ph₃PCHCOCH₂COOC₂H₅ (EAPPY), with HgX₂ (X = Cl, Br and I) in equimolar ratios using methanol as the solvent leads to binuclear complexes of the type [EAPPY·HgX₂]₂ (X = Cl (1), Br (2) and I (3)). Single crystal X-ray analysis reveals the presence of a centrosymmetric dimeric structure containing the ylide and HgX₂ (X = Br or I)_. The IR and NMR data of the product [(EAPPY)·HgCl₂]₂ (1), formed by the reaction of mercury(II) chloride with the same ylide, are similar to those of 2 and 3. Analytical data indicate a 1:1 stoichiometry between the ylide and Hg(II) halide in each of the three products. Theoretical studies indicate that the nature of the R group in ylides of the type Ph₃PCHCOR has a weak effect on the Hg-C(ylide) bond length in binuclear Hg₂L₂I₄ complexes.     

Synthesis of the Anti‐HIV Agent (−)‐Hyperolactone C by Using Oxonium Ylide Formation–Rearrangement

Starting from readily available (S)‐styrene oxide an asymmetric synthesis is described of the naturally occurring anti‐HIV spirolactone (?)‐hyperolactone C, which possesses adjacent fully substituted stereocenters. The key step involves a stereocontrolled Rh^II‐catalysed oxonium ylide formation–[2,3] sigmatropic rearrangement of an α‐diazo‐β‐ketoester bearing allylic ether functionality. From the resulting furanone, an acid‐catalysed lactonisation and dehydrogenation gives the natural product.     

Novel three-component tandem reactions of cyclic mono ketones, isatin and sarcosine: formation of dispiropyrrolidines

One-pot, three-component tandem reactions of cyclic mono ketones, isatin and sarcosine affording dispiropyrrolidines stereoselectively are reported for the first time.     

The Structural Determination of the Ozonides and Their Reaction with Stabilizel Phosphorus Ylides

The ozonides reacted with stabilized phosphorus ylides to give the α,β-unsaturated carbonylcompounds in high yield. The Z/E ratio is dependent on the substituent of the ozonide. Their possiblemechanism was described.     

XYZH systems as potential 1,3-dipoles. Part 62: 1,3-Dipolar cycloaddition reactions of metallo-azomethine ylides derived from α-iminophosphonates

Metallo-azomethine ylides, generated from iminophosphonates in combination with LiBr or AgOAc and bases Et₃N, DBU, t-butyl tetramethylguanidine(BTMG) undergo cycloaddition to give dialkyl pyrrolidine-2-phosphonates along with the corresponding Michael adduct in some cases. Cycloadditions with the chiral dipolarophile 5R-(1′R,2′S,5′R-menthyloxy)-2-(5H)-furanone (MOF) afforded enantiopure cycloadducts.     

Novel Stereoselective Synthesis of (E)-a,b-Unsaturated Esters by the Tandem Reaction of Deprotonation-Oxidation-Wittig Reaction from Phosphonium and Arsonium Salt

Wittigreactionisoneofthemostimportantmethodfortheformationofcarbon-carbondoublebondandhasbeenwidelyusedinthesynthesisofnaturalproducts1,2.Recentlyitwasfoundthatalcoholscanundergoinsituoxidation-Wittigreactionwithphosponiumylidestogivecorrespondingolefinationproducts,whichhasgreatpotentialutilitiesinorganicsynthesis3.Tosimplifytheprocedureofthereactionfurther,weconsideredtocombinethedeprotonationofylide,oxidationofalcoholandWittigreactionintoonetandemreaction.Weutilizedphosphoniumorarsoniumsal…     

Tandem Reaction of Deprotonation-Oxidation-Wittig Reaction: Stereoselective Synthesis of (E)-α,β-Unsaturated Enoates

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A novel access to highly functionalised β-lactams by regio- and stereoselective 1,3-dipolar cycloaddition reaction

A highly regio- and stereoselective synthesis of novel spiro pyrrolidines/pyrrolizidines containing β-lactam and oxazolone moieties under two different conditions is achieved using [3+2] cycloaddition methodology in moderate to good yield.