Reaction of Allenyl Esters with Sodium Azide: An Efficient Synthesis of E-Vinyl Azides and Polysubstituted Pyrroles

Reaction of allene esters with Selectfluor/TMSX (X = I, Br, Cl) and Selectfluor/NH4SCN: Competing oxidative/electrophilic dihalogenation and nucleophilic/conjugate addition

Reaction of benzyl and ethyl allenoates with TMSX (X = I, Br, Cl) and with NH₄SCN were investigated in MeCN, DMF, and in imidazolium ionic liquids [BMIM][NTf₂] and [BMIM][PF₆] as solvent, in the presence and absence of Selectfluor. Comparative product analysis studies demonstrate that the ability of Selectflour to promote oxidative/electrophilic dihalogenation/dithiocyanation with TMSX/NH₄SCN (as observed previously for 1-arylallenes) is diminished in allenoates, most significantly in reactions with TMSCl, and essentially disappearing in reactions with NH₄SCN, in favor of nucleophilic/conjugate addition. The study underscores the contrasting reactivity patterns in 1-arylallenes and allenoates toward electrophilic and nucleophilic additions in halofunctionalization with TMSX/Selectfluor and thiocyanation reactions with NH₄SCN/Selectfluor. These competing pathways are influenced by the nature of the anion, allene structure, and the choice of solvent.

I2-catalyzed synthesis of substituted imidazoles from vinyl azides and benzylamines

A novel and efficient I₂-catalyzed oxidative tandem cyclization of simple vinyl azides and benzylamines has been developed for the synthesis of substituted imidazoles.

Synthesis and anti-protozoal activity of novel dihydropyrrolo[3,4-d][1,2,3]triazoles

1,2,4-Oxadiazole and 1,2,3-triazole containing heterocyclic compounds continue to gain interest in synthesis of chemical entities and exhibit various biological activities as anti-protozoal and anti-cancer agents. By using the principle of bioisosterism, a series of novel oxadiazolyl pyrrolo triazole diones; namely, (3aS,6aR)-1-((3-(4-substituted phenyl)-1,2,4-oxadiazol-5-yl)methyl)-5-phenyl-1,6a-dihydropyrrolo[3,4-d][1,2,3] triazole-4,6(3aH,5H)-diones (5a-k) was designed and synthesized by the 1,3-dipolar cycloaddition reaction of novel 5-azidomethyl 3-aryl substituted 1,2,4-oxadiazoles (4a-k) with N-phenyl maleimide. The structures of all the cycloadducts were elucidated by means of spectroscopic methods and physical characteristics. The in vitro anti-protozoal and cytotoxic activities of these novel heterocyclic compounds were investigated.

Catalyst-free preparation of 1,2,4,5-tetrasubstituted imidazoles from a novel unexpected domino reaction of 2-azido acrylates and nitrones

A highly efficient and convenient method for the synthesis of 1,2,4,5-tetrasubstituted imidazoles from readily accessible 2-azido acrylates and nitrones has been developed. This reaction proceeded under mild conditions without the assistance of any metal, acid, or base.

LIC-KOR-promoted synthesis of alkoxydienyl amines: an entry to 2,3,4,5-tetrasubstituted pyrroles

A stereoselective approach to the synthesis of (E)-alkoxydienylamines (2) is described, starting from alpha,beta-unsaturated acetals (1) and aryl imines, under superbasic conditions. These can be readily converted into alpha-arylglycine derivatives (3) by mild acidic hydrolysis or, in turn, cyclized under oxidative conditions in the presence of a Pd catalyst to 2,3,4,5-tetrasubstituted pyrroles (4).

Selective one-pot synthesis of allenyl and alkynyl esters from beta-ketoesters

A convenient method is described for the dehydration of beta-ketoesters to generate conjugated and deconjugated alkynyl esters and conjugated allenyl esters. This sequential one-pot method involves the formation of a vinyl triflate monoanion intermediate that leads to the selective formation of alkynes or allenes depending on additives and conditions used. Product outcomes appear to be a function of unique mono- and dianion mechanisms which are described.