Spiro-2H-oxocines
The use of o-hydroxycinnamaldehyde as the aldehyde component in spiran synthesis in the case of condensation with the 2,3-trimethyleno-1-benzopyrylium salt led to the production of the first spiran with a conjugated eight-membered ring — spiro(2H-1-benzopyran-3, 3′-trimethyleno-2,2'-2'H-7',8t-benzooxocine). The reaction of o-hydroxycinnamaldehyde and its 5-nitro derivative with 1,3,3-trimethyl-2-methyleneindoline leads to spiro-2H-oxocines in which an additional molecule of the indoline base is connected to the 2H-oxocine ring.