Ultrasound irradiation can promote the 1,3-dipolar cycloaddition reaction of 2-chloropyridinium ylides with 2-benzylidenemalononitrile or 2,2'-(1,4-phenylenebis(methanylylidene))dimalononitrile, to afford the indolizine and bis-indolizine derivatives respectively. While the reaction of pyridinium ylides with 2-benzylidenemalononitrile or 2,2'-(1,4-phenylenebis(methanylylidene))dimalononitrile u...

[reaction: see text] A general strategy for highly enantioselective 1,3-dipolar cycloaddition of diazoesters to beta-substituted, alpha-substituted, and alpha,beta-disubstituted alpha,beta-unsaturated pyrazolidinone imides is described. Cycloadditions utilizing less reactive alpha,beta-disubstituted dipolarophiles require elevated reaction temperatures, but still provide the corresponding pyraz...

Chiral pyrrolidines and pyrrolizidines with spirooxindole ring systems are the central skeletons for numerous alkaloids and pharmacologically important compounds. Gelesmine, pseudotabersonine, formosanine, isoformosanine, morroniside and mitraphylline are some of the alkaloids containing spirooxindole ring systems. Derivatives of spirooxindole find very wide biological applications as anti micr...

An unexpected and interesting intramolecular side reaction occurred during the attempted synthesis of glycosyl cyanides upon treatment of 1-O-acetyl-3-azido-3-deoxyallose derivatives with TMSCN and different Lewis acids. Exo-1,2-O-cyanoalkylidene derivatives formed by neighboring group participation and attack of cyanide underwent, after Lewis-acid mediated isomerization to the endo-isomer, int...

Isosorbide was esterified with acryloyl chloride and crotonic acid yielding isosorbide diacrylate (9a) and isosorbide dicrotonate (9b), which were reacted with benzaldehyde oxime in the presence of zinc(II) iodide and boron triflouride etherate as catalysts to obtain N-alkylated dinitrones 10a/b. Poly(isosorbide itaconite -co- succinate) 13 as a bio-based unsaturated polyester was cross-linked ...

A Diels-Alder cycloaddition approach to the sweroside aglycone intermediate of iridoids was explored using silylated butenolides and levoglucosenone as dienophiles under both Lewis acid and thermal conditions. Results of this study reveal no evidence that using less sterically demanding derivatives compromise the diastereofacial selectivity of the cycloaddition using silylated butenolides. Furt...

Key words (+)-bufogargarizin B - [5+2] cycloaddition Mukaiyama hydration retro-aldol-aldol reaction Suzuki–Miyaura coupling

The rhodium(II)-catalyzed formation of 1,3-dipoles has played a major role in facilitating the use of the dipolar cycloaddition reaction in modern organic synthesis. This is apparent from the increasing number of applications of this chemistry for the construction of heterocyclic and natural product ring systems. This chapter initially focuses on those aspects of rhodium(II) catalysis that cont...

The [4+2] cycloaddition reaction is an enabling transformation in modern synthetic organic chemistry, but there are only limited examples of dedicated natural enzymes that can catalyze this transformation. Thiopeptides (or more formally thiazolyl peptides) are a class of thiazole-containing, highly modified, macrocyclic secondary metabolites made from ribosomally synthesized precursor peptides....

Strain-promoted inverse electron-demand Diels-Alder cycloaddition (SPIEDAC) reactions between 1,2,4,5-tetrazines and strained dienophiles, such as bicyclononynes, are among the fastest bioorthogonal reactions. However, the synthesis of 1,2,4,5-tetrazines is complex and can involve volatile reagents. 1,2,4-Triazines also undergo cycloaddition reactions with acyclic and unstrained dienophiles at ...