Theoretical investigation on Iodine (III)-Mediated Selective Csp−Csp2 bond Cleavage from Nitrogenation of alkyne with Nitrone Yielding Functionalized [1,4] Oxazinone

Our DFT calculations provide the first theoretical investigation on iodine(III)-mediated selective Csp−Csp2 bond cleavage of 1-alkynylnaphthol with N-phenyl nitrone. 1-alkynylnaphthol was isomerized to VQM under base NEt3, which underwent [4 + 3] cycloaddition with N-phenyl nitrone affording heptatomic ring. 1,3-rearrangement of N−O vinyl group was determined to be rate-limiting furnishing another heptatomic ring more stable. The ring opening and sequential hydrogen shift gave iminium. The intramolecular 1,4-addition delivered pyrroline through pentacyclic alkene. The intermolecular alcoholysis with MeOH and PhI(OAc)2 pro-vided α-aminoketone. Via oxidative dearomatization and intramolecular cyclization, spirolactam was formed followed by ring opening and ester exchange producing major product [1,4]oxazinone. Alternatively, the in-tramolecular 1,2-addition of O-anion resulted in bridged ring by-product. The positive solvation effect is suggested by decreased absolute and activation energies in solution compared with in gas. These results are supported by Multiwfn analysis on FMO composition of specific TSs, and MBO value of vital bonding, breaking.