Acid-catalysed ring expansion reactions of cyclobutane derivatives bearing a vicinal substituted-diol group give a-aryl and a-vinyl substituted cyclopentenones in good yields. ... We report here two of the new methods that we have developed recently for the preparation of oc-aryl- and a-vinyl-cyclopen- tenones. The syntheses start with the high-yield preparation of the cyclobutanone (2) by an aldol-type coupling of acetals with the cyclobutene (1) with ...