Regioselective Dearomatization of <i>N</i> ‐Alkylquinolinium and Pyridinium Salts under Morita‐Baylis‐Hillman Conditions
Abhishek Pareek, Marcin Kałek
Abstract
Abstract Morita‐Baylis‐Hillman reaction employing N ‐alkylquinolinium salts as electrophiles has been developed. The reaction is promoted by DBU, which acts both as a catalyst activating the electron‐poor olefin as well as a base. The dearomatization occurs regioselectively at the C‐2 position, delivering a broad range of α‐(1,2‐dihydroquinolin‐2‐yl)vinyl esters, ketones, and sulfones. The scope of the transformation has also been extended to N ‐alkylpyridinium salts. For this class of substrates a presence of at least moderately electron‐withdrawing substituent in the ring is necessary to attain good reactivity. In particular, N ‐alkylpyridinium salts containing an ester group undergo the dearomatization regioselectively at the C‐4 position, while nitrile and nitro moieties cause the non‐selective formation of products of the C‐2 and C‐6 additions. magnified image