Process for producing compounds useful in perfumery including isochromans and acylated indane hydrocarbons with an alkylene oxide or with a lower acyl halide in the presence of a hydrocarbon or hydrocarbon mixture containing C.sub.5 to C.sub.10 alkanes at a temperature of from -20.degree. C. up to -5.degree. C. In the case of forming isochromans, the resulting alcohol is reacted, in situ, with a lower alkanol and a formaldehyde precursor at temperatures of from 20.degree. C. up to 80.degree. C.