Luisa Garanti

MeOPEG-bounded azide cycloadditions to alkynyl dipolarophiles

Abstract The MeOPEG-supported azide 2 was reacted in the presence of a number of alkynyl dipolarophiles. The corresponding 1-MeOPEG-supported-1,2,3-triazoles were obtained in nearly quantitative yields. Acidic hydrolysis of the cycloadducts 5b and 6b caused the removal of the MeOPEG pendant giving 4-methoxycarbonyl-1,2,3-triazole 9 and 5-methoxycarbonyl-1,2,3-triazole 10 , respectively.

The first case of asymmetric induction in intramolecular nitrile imine cycloadditions: synthesis of enantiopure 3-substituted 6-oxo-2,3,3a,5-tetrahydro-4-carbomethoxy-furo[3,4-c]pyrazoles

Abstract Intramolecular cycloaddition of homochiral nitrile imines 5 , generated in situ from base treatment of the corresponding hydrazonoyl chlorides 4 , involves diastereoselective formation of the title compounds in the enantiomerically pure form.

Stereoselective intramolecular cycloadditions of homochiral nitrile imines: synthesis of enantiomerically pure 3,3a-dihydro-pyrazolo[1,5-a][1,4]benzodiazepine-6(4H)-ones

Abstract Starting from the commercially available ( S )-1-phenylethylamine, we have synthesised the homochiral hydrazonoyl chlorides 4 . The intramolecular cycloaddition of the corresponding nitrile imines 5 gave the diastereoisomeric 3,3a-dihydro-pyrazolo[1,5- a ][1,4]benzodiazepine-6(4 H )-ones 6 and 7 in enantiopure form.

SYNTHESIS OF BIS-(3,5)PYRAZOLOPHANES BY SEQUENTIAL INTERMOLECULAR-INTRAMOLECULAR NITRILIMINE CYCLOADDITIONS

Abstract A series of bis-(3,5)pyrazolophanes of potential interest in supramolecular chemistry have been synthesized by exploiting sequential intermolecular-intramolecular cycloadditions of properly functionalised nitrilimines.

Medium- and large-ring heterocyclic systems by intramolecular nitrile imine cycloadditions

A series of hydrazonyl chlorides bearing an alkenyl chain have been synthesised and treated with silver carbonate. The propensity of the so-formed nitrite Imine intermediates to undergo intramolecular cycloaddition is markedly dependent on the length and the flexibility of the chain. The latter also affected the regio- and the stereo-chemistry of the Intramolecular process. In certain circumstances, tandem intermolecular–Intramolecular cycloadditions took place, to produce largering heterophanes.

Diastereoselective cycloadditions of nitrilimines to enantiopure acrylamides

The diastereoselective cycloaddition of the nitrilimine 2 with enantiopure acrylamides 3 was exploited to obtain enantiopure 4,5-dihydropyrazoles 4 and 5. Basic hydrolysis of the cycloadducts gave the dicarboxy derivatives 6 and 7 or 8 and 9, which are of potential interest as new chiral building blocks.

Stereoselective intramolecular cycloadditions of homochiral N-alkenoyl aryl azides

Abstract Starting from the commercially available (S)-1-phenylethylamine and l -alanine benzylester, we synthesised the homochiral N-alkenoyl aryl azides 2a–2d. The intramolecular cycloaddition of unsubstituted 2a and 2b gave enantiopure 3,3a-dihydro-1,2,3-triazolo[1,5-a][1,4]benzodiazepine-4(6H)-ones 3a, 3b, 4a and 4b, while phenyl-substituted 2c and 2d gave enantiopure 1,1a-dihydro-2H-azirino[2,1-c][1,4]benzodiazepine-4(6H)-ones 5c, 5d, 6c and 6d.

Asymmetric induction by the (S)-1-phenylethyl group in intramolecular nitrile imine cycloadditions giving enantiopure 3,3a-dihydro-pyrazolo[1,5-a][1,4]benzodiazepine-4(6H)-ones

Abstract Stereoselective intramolecular cycloadditions of homochiral nitrile imines 5 are described as a fruitful source of enantiopure 3,3a-dihydro-pyrazolo[1,5-a][1,4]benzodiazepine-4(6H)-ones 6 and 7.

Synthesis of pyrazole-containing azacrown ethers by intramolecular nitrilimine cycloadditions

Abstract Intramolecular cycloadditions of suitably functionalised nitrilimines have been exploited to prepare a number of crown azaethers having a medium or large ring annulated to pyrazole unit(s).

Synthesis of [1,2,3]triazolo[1,5-a][4,1]benzoxazepines via intramolecular azide cycloaddition

Starting from isatoic anhydride and propargyl alcohols, we developed a synthetic approach to the title compounds, where the key step is an intramolecular cycloaddition of the azido group onto the acetylenic bond