2-(1,2,6,7-Tetrahydro-8H-indeno[5,4-b]furan-8-ylidene)acetonitrile; (1,2,6,7,-Tetrahydro-8H-indeno[5,4-b]furan-8-ylidene)acetonitrile; (E)-2-(1,2,6,7-Tetrahydro-8H-indeno[5,4-b]furan-8-ylidene)acetonitrile