The intramolecular Diels-Alder reactions of 2,3-dimethylene-2,3-dihydrofurans have been investigated through the pyrolysis of 2-alkenyl-3-furylmethyl benzoates. Under FVP conditions each of the 2,3-dimethylene-2,3-dihydrofurans can undergo an intramolecular Diels-Alder reaction or 1,5-hydrogen shift to give the corresponding tricycles 4c,t, 5c,t, and 6c,t and 1,5-hydrogen shift products 36c,t and 37c,t;FVP of 1,5-dibenzocyclooctadienes containing heteroatoms and dibenzosuberanes gave the corresponding tricyclic compounds benzodifuran (18), acridine (24), and anthracene with exception of 6H,11H-dibenzo b,f 1,4 -dioxocin (17). The FVP of 17 gave (2-hydroxybenzyl)-o-benzaldehyde (28) as a major product;A mechanistic study of the regiospecific formation of 9-methyl- anthracene from the sealed tube pyrolysis the 4+4 dimer of o-xylylene (1) is presented. This study was carried out by pyrolyzing several possible precursors for 9-methylanthracene (e.g., 5,6-dihydrodibenzo a,e cyclooctene, di-o-tolylethane, and 5-methyl- dibenzosuberane). Sealed tube pyrolyses of dibenzosuberanes and dibenzosuberones were also carried out;A new method of preparing cyclopentadienones by the pyrolysis of cyclic diethers is presented. Cyclopentadienones including inden-2-one have been utilized in the synthesis of polycyclic compounds;The transient existence of these intermediates has also been proven by the isolation of polycyclic compounds; *DOE Report IS-T-1293. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.