A process for preparing 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran which comprises subjecting o-methallyloxyphenol to a rearrangement and cyclization reactions in the presence of, as a catalyst, aluminum halide and N-substituted aniline derivative, or a complex of both these compounds.
Stable polyisocyanate prepolymers containing hydroxy functions, consisting of products of polyaddition of at least one organic polyisocyanate to at least one product of condensation (A) of an alkylene oxide with an amine, in the presence of at least one polyol (B) containing free hydroxy functions, in which the said polyol (B) contains primary hydroxy functions and has a molecular weight greater than or equal to 3,000. The process for their manufacture consists in reacting, at a temperature between 10.degree. and 150.degree. C., and more usually between 20.degree. and 80.degree. C., the mixture of at least one organic polyisocyanate, at least one condensation product (A) and at least one polyol (B).
