Alkenes benzofurans from

Claisen rearrangement of allyl phenolic ethers, followed by oxidation of the alkene generates ortho-hydroxy-arylacetaldehydes which close to give benzofurans under acid catalysis, the example showing the synthesis of 8-methoxypsoralen (33.8.1)7 The formation of 2-substituted benzofurans from 2-(ortho-hydroxyaryl)-ketones is also very easy. ... 

The cyclisations and cycloadditions reported include the synthesis of benzofuranes from halophenols and alkynes,343 the generation of y-butyrolactams from chloroformamides,344 the intramolecular ring-closure to spirocyclic amides345 and the [3+2] cycloaddition of trimethylene methane precursors to a,p-unsaturated aldehydes,345 imines347 and activated alkenes (eq.33).348... 

A variety of heterocyclic compounds of the indole and benzofuran type can be made via photoaddition of alkenes to 2-amino- or 2-hydroxy-1,4-naphthoquinone. These products, described by H. Suginome probably derive from an intramolecular trapping reaction of the intermediary 1,4-biradicals or 1,4-zwitterions. 

Indole and isoquinolone nuclei are prominent structural units frequently found in numerous natural products and pharmaceutically active compounds. Thus, the search for new methodologies to obtain these scaffolds with different substitution patterns is a current major objective in organic synthesis. Similar to benzofuran synthesis, Aluraez et al. observed that the palladium-catalyzed cascade intramolecular alkyne aminopaUadation/intermolecular Heck-type coupling reaction under oxidative conditions is an efficient methodology for the synthesis of indole 217 and isoquinolone 219 derivatives, starting from readily available aniline 216 or benzamide 218 substrates and functional alkenes [77] (Scheme 6.60). 

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