Photochemical ring enlargement of macrocyclic N-phenyl imides into cyclophanes

Allylic N-phenyl imides containing 12- and 14-membered rings, such as compo unds 3 and 12, are easily synthesized by ring enlargement from cycloalkanon es and phenyl isocyanates. Irradiation of 3 and 12 in EtOH and MeCN, with h igh- and low-pressure Hg lamps,led, via the photo-Fries rearrangement, to t he same primary products: the orthocyclophane 8 and the paracyclophane 9 fr om 3 (Scheme 2), and the corresponding compounds 13 and 14 from 12 (Scheme 3). Besides the primary photorearrangement products, secondary products, th e aminocyclophanes 10 and 11, or 15 and 16, respectively, were also formed. The total yields of the four products were very high when the N-phenyl imi des were irradiated in MeCN with a low-pressure Hg lamp: 97 and 93%, respec tively If the pam-position in 3 or 12 is blocked by a Me group, the para-ph oto-Fries rearrangement is prevented. In this case, only one primary photop roduct is formed: the corresponding orthocyclophane (17 or 23, resp.). The most remarkable result was observed on irradiation of the 12-membered N-(4- tolyl) imide 5 in MeCN (low-pressure lamp). It reacted nearly quantitativel y to give only two products: 15-methyl-1-aza[12]orthocyclophane-2,12-dione (=16-methyl-2-azabicyclo[12.4.0]octadeca-1(14),15,17-triene-3,13-dione; 17) in 80% yield and 17-amino-14-methyl [11]metacyclophane-1, 11-dione (= 17-a mino-15-methylbicyclo[11.3.1]heptadeca-1(17),13,15-triene-2,12-dione; 19) i n 16% yield (Scheme 5).