The mass spec tra of a se ries of N-aryl , -un sat u rated -lac tams were stud ied. Be sides the mo lec u lar ion, the three char ac ter is tic frag ments such as [M -82] were com monly found in a se ries of N-Aryl , -un sat u rated -lac tams in EI/MS. Fur ther more the mech a nism for the in ter pre ta tion of these fragments is also de scribed.
IN TRO DUC TIONOnly a few meth ods for the syn the sis of N-aryl , -unsat u rated -lac tams, a key in ter me di ate for mitomycin, have been re ported in the lit er a ture.1 Un til the pres ent, only a lit tle at ten tion was paid to the EI-MS of these lac tams. 2 A de tailed de scrip tion of these char ac ter is tic fragmental be hav iors is still lack ing. Re cently we have de vel oped a new route for N-aryl , -un sat u rated -lac tams via the ring-closing metath e sis re ac tion. Herein we would like to re port and in ter pret these frag ments by a ra tio nal pro posed mech a nism. This re sult is ex pected to be use ful in for ma tion for fur ther iden ti fi ca tion of N-aryl , -un sat u rated -lac tams.
EX PER I MEN TAL SEC TIONThe N-ary , -un sat u rated -lac tams (1a-f) for mass spec tral stud ies were pre pared by our pre vi ously re ported meth ods 3 by treat ing N-aryl 3-(phenylsulfonyl)propanamide with two equiv a lents of tert-butoxide and 1 equiv a lent of allyl bro mide to af ford N-allyl N-aryl alkenamides. The result ing N-allyl N-aryl alkenamides were treated with Grubbs cat a lyst to un dergo the ring-closing me tath e sis (RCM) to give the de sired com pounds, N-aryl , -un sat u rated -lactams. Mass data were re corded on a Hewlett Packard mass spec trom e ter con nected to a Hewlett Packard se ries II model gas-liquid chromatograph. It was equipped with a 12 m 0.
RE SULTS AND DIS CUS SIONIn gas chro ma tog ra phy N-aryl , -un sat u rated -lactams both 1a-c and 1d-f showed a reg u lar in crease in re tention time as the mo lec u lar weight in creases. The re ten tion time and char ac ter is tic peaks (m/z ) of N-aryl , -un sat u rated -lac tams in gas chro ma tog ra phy and EI-MS are given in Table 1 .In EI-MS N-aryl , -un sat u rated -lac tams (1a-f) always ex hibit the mo lec u lar ion peak as a base peak, no mat ter what kinds of sub stitu ents ex ist on the ben zene ring. It was also ob served that [M-29] + and [M-82] + ion peaks of 1c have much lower rel a tive in ten sity com pared to those of 1a-b and 1d-f, per haps due to the pres ence of a methoxy group on the para po si tion of the ben zene ring. The rel a tive in ten sity of
