An unsaturated carbonyl compound, for example, one expressed by the following formula, ##STR1## is prepared by maintaining at an elevated temperature a novel allyl acetal of a .beta.,.gamma.-unsaturated aldehyde, for example, one expressed by the following formula ##STR2## The allyl acetal can be derived, for example, for 3-methyl-3-butenal-1 having 5 carbon atoms and prenyl alcohol having 5 carbon atoms. Thus, the unsaturated aldehyde having the increased number of carbon atoms can be formed in a high yield by a relatively simple reaction.
一种不饱和羰基化合物,例如以下式子所表示的化合物:##STR1## 通过在高温下维持一种新的β,γ-不饱和醛的
丙烯醇缩醛来制备,例如以下式子所表示的化合物:##STR2## 这种
丙烯醇缩醛可以由具有5个碳原子的3-甲基-
3-丁烯醛和具有5个碳原子的
异戊烯醇衍生而来。因此,通过相对简单的反应,可以高产率地制备具有更多碳原子的不饱和醛。