10.1055/s-1986-31727
The research focuses on the reaction of benzoxa(thia)zoles with allenylmagnesium bromide, aiming to synthesize propargylbenzothiazolines and dipropargylalkyl-o-aminophenols. The study explores the reactivity of these heterocycles with organometallic reagents, specifically the allenyl(propargyl) Grignard reagent, which is expected to behave as an allylic Grignard due to its ambident nature. The researchers found that benzoxazoles could be readily converted to dipropargylalkyl-o-aminophenols, while benzothiazoles reacted to form propargylbenzothiazolines and, in one case, a 2-allenylbenzothiazole. The reactions were proposed to proceed via an S_N2' mechanism, with the formation of intermediate benzoxa(thia)zoline, which could then lead to ring-opened products or further react with the Grignard reagent. Key chemicals used in the process include benzoxazoles (2a-e), benzothiazole (4a), allenylmagnesium bromide (1), and 2-methoxybenzothiazole (8). The study concludes with the successful synthesis of these novel compounds, which could be used for the synthesis of tricyclic dienes and phenols fused with S-membered rings.