3.4- Dihydroiso-coumarins

The reaction of o-cyanobenzyllithium, generated by Te-Li exchange in the corresponding telluride, with aldehydes or ketones followed by acid, promotes lactonization of the obtained hydroxyderivatives, affording 3,4-dihydroiso-coumarins compounds. ... 

Hydroxy-l-methoxyallenyl-4,4-dialkylisochromans, available from dihydroiso-coumarins, undergo a Pd(0)-catalysed ring expansion to benzoxepanones. In the absence of the Pd catalyst, the dihydroisocoumarins can be converted direetly into a benzoxocanone (Scheme 20) <04SL481>. 

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