Benzenoid catafusenes: Perfect matchings, isomerization, automerization
It the polyc,ycl i of Kekule str The structure 4- and 3-peri tic isomeriza is shown that for a given number h of b enzenoid rings, c aromatic hydrocarbons with the maximum number K(max) ,uctures (or of perfect matchings) are cata-condensed. s of such catafusenes with K(max) present interesting odicities in terms of h. By analogy w ith known cataly- tions of benz(a)anthracen e into chrysene, 1.e. of a catafusene with a smaller number of perfect matchings into one with a higher number, it was inferred in 1965 that degenerate rearrange- ments (automerizations ) of catafusenes may be possible, and this was demonstrated thermally in 1977 by Scott. Data for the AlHal3-cataly- zed automerization of phenanthrene labeled with carbon-13 are re- viewed, and the reaction mechanism is discussed. Prospects for new thermal or catalytic isomerizations or automerizations of catafuse- nes are considered.