Stable nitrile oxide dipolar cycloadditions in pure water

A systematic study on the behaviour of stable 2,4,6-trimethyl-3,5-dichlorobenzonitrile oxide versus a number of mono-, bi- and trisubstituted dipolarophiles in water was pursued obtaining simple as well as annulated isoxazolines. Reaction conditions changed with the dipolarophilic species, according to their solubility in water and the degree of substitution of the reactive carbon\u2013carbon multiple bond. The presence of sodium dodecylsulfate was also tested as potential micellar catalyst

Light harvesting of CdSe/CdS quantum dots coated with b-cyclodextrin based host-guest species through resonant energy transfer from the guests

Films of nano-hybrids based on red emitting CdSe/CdS QDs functionalized with perthiolated \u3b2-cyclodextrin hosting a green emitting nitrobenzoxadiazole derivative show emission harvested by the host\u2013guest organic system through resonant energy transfer from the organic host\u2013guest species to the QD

Light harvesting of CdSe/CdS quantum dots coated with β-cyclodextrin based host–guest species through resonant energy transfer from the guests

Films of nano-hybrids based on red emitting CdSe/CdS QDs functionalized with perthiolated \u3b2-cyclodextrin hosting a green emitting nitrobenzoxadiazole derivative show emission harvested by the host\u2013guest organic system through resonant energy transfer from the organic host\u2013guest species to the QD

Thieno[2,3-f]triazolo[1,5-a][1,4]diazepines and Thieno [2,3-f]triazolo[1,5-a][1,4]oxazepines from Azide Cycloaddition

Intermolecular dipolar cycloadditions between 2-methoxycarbonyl-3-thenylazide (3) and monosubstituted dipolarophiles bearing a triple carbon-carbon bond were exploited in a three step synthesis of the title compounds. The intramolecular cycloaddition of substituted thenylazide (11) was also carried out in the two-step synthesis of the thieno[2,3-f][1,2,3]triazolo[1,5-a]-[1,4]diazepine derivative (8)

1,3-Dipolar cycloadditions of MeOPEG-bounded azides

1,3-Dipolar cycloadditions of MeOPEG-supported azide 2 with a variety of dipolarophiles have been studied. 1-MeOPEGsupported 1,2,3-triazoles 4 and 5, 1,2,3,4-tetrazoles 12 and aziridine 14 were obtained in nearly quantitative yields. The removal of the MeOPEG moiety from the 1,2,3-triazole nucleus was achieved by acidic cleavage of the cycloadduct mixtures 4 and 5 giving 4- and 5-substituted-1,2,3-triazoles 6 and 7

A short synthesis of enantiopure 2-substituted 4,5-dihydro-1,4-benzodiazepin-3-ones via intramolecular azide cycloaddition

Starting from the appropriate azides bearing the (S)-1-phenylethylamine and the l-alanine benzylester as chiral pendants, a facile and effective synthetic route to the title compounds in their enantiopure form was developed with excellent product yields obtained. Basic hydrolysis of the ester group of title compounds 3a\u2013c gave the corresponding, readily functionalisable carboxylic acids. Catalytic reduction of 2-benzyl derivatives 3c and 3f gave 4-functionalised 1,2,4,5-tetrahydro-1,4-benzodiazepin-3-ones in enantiopure forms

Nitrilimine cycloadditions to the cyano group in aqueous media

Dipolar cycloadditions between nitrilimines (2) and the cyano group of activated nitriles (3) were exploited in aqueous sodium hydrogencarbonate as reaction media in the presence of a surfactant. Short reaction times and mild conditions were experienced affording 1-aryl-5-substituted 1,2,4-triazoles

Stereoselective synthesis of highly functionalised tricyclic \u3b2-lactams via intramolecular nitrilimine cycloaddition

The novel azeto[2',1':1,2]pyrrolo[3,4-c]pyrazole skeleton has been obtained in both racemic and enantiopure forms by means of intramol. cycloaddn. of nitrilimines. Fully stereoselective cycloaddns. were obtained, giving tricyclic b-lactams I (R = H, Me) as single diastereoisomers with good overall yields

A bicyclo[3.1.1]heptano[4,3-c]pyrazole derived chiral auxiliary for dipolar cycloadditions

Starting form naturally occurring (S)-cis-verbenol 1 and (1R)-( )-myrtenol 2, we synthesised enantiopure bicyclo[3.1.1]heptano[4,3-c]pyrazole derivatives 7 and 8 via a stereoselective nitrilimine cycloaddition as the key step. The effectiveness of the above skeleton as a new chiral auxiliary was evaluated towards the 1,3-dipolar cycloadditions of nitrile oxides and nitrilimines. Basic hydrolysis of the major cycloadducts gave enantiopure 5-carboxy-4,5-dihydroisoxazole (S)-(+)-19 and 5-carboxy- 4,5-dihydropyrazole (S)-(+)-20, respectively, which are of potential interest as chiral building blocks