Verb + infinitive, no preposition
oser
no preposition
The constructions
no prepositionoser + infinitif
Il n'ose pas parler en public.
Do not writeIl n'ose pas de parler en public.
Why
Oser is built directly: oser demander, oser dire. Its everyday opposite, hésiter à, takes à. Two verbs close in meaning, two constructions.