Heterocycle‐bridged and Conformationally Constrained Retinoids: Synthesis of 4‐(7,8,9,10‐Tetrahydro‐7,7,10,10‐tetramethyl‐4H‐benzo[6,7]chromeno‐ [4,3‐d]thiazole‐2‐yl)benzoic Acid

Abstract

Retinoids are a class of synthetic and natural compounds structurally related to retinoic acid. In a search for discovery of a new class of heterocycle‐bridged and conformationally constrained retinoids, here we report the synthesis of 4‐(7,8,9,10‐tetrahydro‐7,7,10,10‐tetramethyl‐4H‐benzo[6,7]chromeno[4,3‐d]thiazole‐2‐yl)benzoic acid (10) starting from 5,6,7,8‐tetrahydro‐5,5,8,8‐tetramethylnaphthalen‐2‐ol (13). Several approaches was attempted to obtain target compound 10. Structure elucidation of synthesized compounds has been made on the basis of elemental analysis and spectral data (1H NMR, IR and MS).

Metal-Free Oxidative Annulation of Phenols and Amines: A General Synthesis of Benzoxazoles

“…To a stirring solution of 2,5-dichloro-2,5-dimethylhexane (4 g, 21.84 mmol) and phenol (2.1 g, 21.84 mmol) in dried dichloromethane (24 mL), aluminum chloride (988 mg, 0.33 mmol) was added over 15 min . After stirring for an additional 30 min at room temperature, the reaction mixture was refluxed for 45 min.…”

“…Compound 14a was prepared in accordance with the general procedure ( 3 ) using 2,5-dichloro-2,5-dimethylhexane (4 g, 21.84 mmol), phenol (2.1 g, 21.84 mmol), and aluminum chloride (988 mg, 0.33 mmol) in dried dichloromethane (24 mL) . It was purified by silica-gel column chromatography using petroleum ether/ethyl acetate (10/1) as an eluent and isolated as a white powder.…”