Polyalkylpiperidine compounds of the formula I ##STR1## in which Y is the group ##STR2## are very effective stabilizers for organic materials.

The invention relates to a process for the preparation of polyalkyl-1-oxa-diazaspirodecane compounds, which can be used as highly active light stabilizers for polymers. The reaction is carried out in an inert organic solvent in the presence of solid alkali metal hydroxide or of the corresponding amount of a mixture of solid alkali metal hydroxide and water as the sole catalyst. The process offers the advantage that, by changing the reaction procedure in a multiphase system and avoiding the use of a phase transfer catalyst, equally good results are achieved with regard to product quality and yield. Additionally, it is possible to reduce the reaction time from over 6 hours to 30 minutes. This results in a considerable rise in the space-time yield and consequently contributes, in addition, to an increase in the economy of the process of the invention.

Polyalkylpiperidine compounds of the formula I ##STR1## in which Y is one of the groups ##STR2## are distinguished by very low volatility at elevated temperature and are very effective stabilizers for organic substances.