A novel halogen-free synthesis of benzo-fused six-membered 1,4-heterocycles through the chemistry of dialkyl carbonates is reported. Commercially available catechol, 2-aminophenol, and 2-aminothiophenol were reacted first with ethylene carbonate in an autoclave to give O -hydroxyethyl, N -hydroxyethyl, and S -hydroxyethyl derivatives respectively, through a B Al 2 mechanism. Then 2-(2-hydroxyethoxy)phenol and 2-(2-hydroxyethylamino)phenol were cyclized in excellent yields by reaction with dimethyl carbonate (DMC) and DABCO as a bicyclic organic base to give the corresponding benzodioxine and benzoxazine derivative, respectively. Moreover, 2-(2-aminophenylthio)ethanol afforded the benzothiazine derivative in good yield by reaction with DMC with an excess of a strong base such as NaH. The investigation on the cyclization reaction has highlighted that several equilibria are involved leading to the formation of carbonate and carbamate intermediates through B Ac 2 mechanisms. Depending on the reaction conditions employed, these intermediates may undergo either kinetic-controlled ring closure by a B Al 2 mechanism or by-product formation.
Autori: | Aricò, Fabio (Corresponding) | |
Data di pubblicazione: | 2019 | |
Titolo: | Benzo-Fused 1,4-Heterocycles via Dialkyl Carbonate Chemistry | |
Rivista: | SYNTHESIS | |
Digital Object Identifier (DOI): | http://dx.doi.org/10.1055/s-0037-1611710 | |
Volume: | 51 | |
Appare nelle tipologie: | 2.1 Articolo su rivista |
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