| Abstract: | Fragmentation upon electron impact of cinnoline (1) occurs with the consecutive loss of N2 and C2H2. Fragmentation of 4,4′-dicinnolyl (2) and 4-styrylcinnoline (4) gives a series of ions leading to the “dibenzoladderene” ion (3) and the 1-phenylbenzodibutylene ion (5) respectively. Fragmentation of 4-styrylquinoline (6) also leads to 5 , but of more interest is the loss of H. during ring rearrangement to give the highly resonance stabilized 3-styrylbenzocyclo-pentadieneoneimine ion (7) which then loses N. Fragmentation of various other substituted cinnolines follow different pathways: 4-methylcinnoline (8) apparently fragments through the “1,2-diazatropylium” ion (9) ; nitrocinnolines fragment with initial loss of the nitro substituent; aminocinnolines fragment with initial loss of N2; and 4-cinnolone (17) fragments with the consecutive loss of two HCN's and CO. The NMR spectra of cinnolines generally show the following order of deshielding: 3-proton > 8-proton > 4-proton. The spectra of cinnolinum chloride (18) is interpreted in terms of protonation at N-1 of 1 , and the spectrum of 17 is interpreted in terms of strong intermolecular hydrogen bonding. |
