From β-Nitrothiophenes to Ring-Fused Nitrobenzenes: An Overall Ring-Enlargement Process via a Facile, Aromatization-Driven, Thermal 6π Electrocyclization1

Connecting a carbonyl and a π-conjugated group through a p-phenylene linker by (5+1) benzene ring formation

A benzene ring was formed to connect a carbonyl group of various methyl ketones with a π-conjugated group through a p-phenylene linker. Methyl ketones and streptocyanines were used as the C1 and C5 sources, respectively, in the (5+1) annulation, which could form donor-π-acceptor molecules.

De novo synthesis of multisubstituted aryl amines using alkene cross metathesis

The olefin cross-metathesis reaction allows rapid access to 1,5-dicarbonyl intermediates which, upon treatment with a primary or secondary amine, allow the synthesis of a range of multisubstituted carbocyclic aryl amines. This de novo arene synthesis yields nonclassical substitution patterns in a regioselective and predictable approach that is compatible with several functional groups.

Oxidative Nucleophilic Substitution of Hydrogen versus Ring-Opening in the Reaction of 4-R-2-Nitrothiophenes with Amines. The Crucial Effect of 4-Alkyl Groups

4-Alkyl-2-nitrothiophenes [10: R = CH3, CH(OH)CH3, CH(OCH3)CH3] react with secondary aliphatic amines, in the presence of AgNO3, to give 3-alkyl-2-amino-5-nitrothiophenes (12) through an oxidative nucleophilic substitution of hydrogen (ONSH) of synthetic interest. This behavior is in striking contrast with that of the parent 2-nitrothiophene (6), which was found to undergo ring-opening in analogous reaction conditions. A possible rationale for the crucial effect of alkyl groups is suggested, grounded also on a study of the corresponding Meisenheimer-like adducts.