Synthesis of 1,1‐Dimethyl‐4‐indanol Derivatives

Abstract

The synthesis of 1,1‐dimethyl‐4‐indanols (3a,b) has been achieved by intramolecular Friedel–Crafts cyclization of 2‐(3‐methyl‐2‐butenyl)phenols (5a,b) or 1‐methoxy‐2‐(3‐methyl‐2‐butenyl)benzenes (6a,b) followed by demethylation, respectively.It was found that the solvent was critical for the formation of different products in the intramolecular Friedel–Crafts reactions of 6. The unexpected product 4‐methoxy‐1,1,6,6‐tetramethyl‐as‐hydrindacene (11) was obtained from the Friedel–Crafts reactions of 6a, and its structure was confirmed by X‐ray diffraction analysis. The key intermediates 5a,b were prepared by ortho‐alkenylation of phenols with 1‐bromo‐3‐methyl‐2‐butene, and the reaction temperature exerted an obvious impact on the yield of 2‐(3‐methyl‐2‐butenyl)phenol (5a).

Keywords:

• 1,1‐Dimethyl‐4‐indanols
• intramolecular Friedel–Crafts reactions
• 1‐methoxy‐2‐(3‐methyl‐2‐butenyl)benzenes
• ortho‐alkenylation of phenols

Acknowledgment

This research was supported by the grants from the National Natural Science Foundation of China (No. 20272010 and 30200348) awarded to P. Xia and Y. Chen, respectively, and the research grant (2002046069) for PhD program from the National Education Administration of China awarded to P. Xia.