Synthesis, characterization, and DFT studies of novel spiroacenaphthylene‐1,3‐oxazines

Abstract

AbstractThe novel spirocyclic 1,3‐oxazino and 1,2′‐pyrido systems were synthesized by [4 + 2] cycloaddition reaction between Huisgen 1,4‐dipoles (isoquinoline‐acetylenic esters and quinoline‐acetylenic esters) with the C═O and C═C (CN)2 double bonds of acenaphthoquinone‐malononitrile adduct. The major product was the 1,3‐oxazino derivative. The structure of a typical product was confirmed by X‐ray crystallography. The B3LYP/6‐31G(d) density functional theory calculations for carbon atom charge of keto‐carbonyl group and its adjacent carbon atoms show that the carbonyl group is much more electrophilic. The major and minor products possess 2 stereogenic centers; thus, 2 diastereomers are possible for each compound. The calculated energy difference between [(1R,11bS)/(1S,11bR)] and [(1R,11bR)/(1S,11bS)] diastereomers of major product is 8.8 kcal/mol, while the more stable diastereomer of minor product [(1S,11bS)/(1R,11bR)] is calculated to have 9.9 kcal/mol lower energy than [(1S,11bR)/(1R,11bS)] isomer. The diastereoselectivity, good yields, and lack of activator or metal promoters are the main advantages of this approach.