1. Brazilein (6a,7-dihydro-3,6a,10-trihydroxy-benz[b]indeno[1,2-d]pyran-9(6H)-one, Fig

2. 20 Rare earth chlorides were used to catalyze the synthesis of 2-butoxy- 4-dihydro-2H-pyran using equimolar acrolein and vinyl butyl ether.

3. The invention relates to photochromic anellated naphthopyrans having a benzene ring which is adjacent to the pyran acid and is linked to the para substituents via both meta positions, and to use thereof in plastics of all types, in particular for ophthalmic purposes.