Catalyst-free synthesis of substituted pyridin-2-yl, quinolin-2-yl, and isoquinolin-1-yl carbamates from the corresponding hetaryl ureas and alcohols?

Organic & Biomolecular Chemistry Pub Date: 2021-06-10 DOI: 10.1039/D1OB00783A

Abstract

A novel catalyst-free synthesis of N-pyridin-2-yl, N-quinolin-2-yl, and N-isoquinolin-1-yl carbamates utilizes easily accessible N-hetaryl ureas and alcohols. The proposed environmentally friendly technique is suitable for the good-to-high yielding synthesis of a wide range of N-pyridin-2-yl or N-quinolin-2-yl substituted carbamates featuring electron-donating and electron-withdrawing groups in the azine rings and containing various primary, secondary, and even tertiary alkyl substituents at the oxygen atom (48–94%; 31 examples). The DFT calculation and experimental study showed that the reaction proceeds through the intermediate formation of hetaryl isocyanates. The method can be applied to obtain N-isoquinolin-1-yl carbamates, although in lower yields, and ethyl benzo[h]quinolin-2-yl carbamate has also been successfully synthesized (68%).

Graphical abstract: Catalyst-free synthesis of substituted pyridin-2-yl, quinolin-2-yl, and isoquinolin-1-yl carbamates from the corresponding hetaryl ureas and alcohols
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