title: Green approach to stereoselective synthesis of benzo[d]chromeno[3,4- h]oxathiazonine derivatives via MCRs in water: a combined experimental and DFT study.
abstract: (7S, 14S, 16R)- dialkyl 6-oxo-6,7,13,14-tetrahydro-7,14-methanobenzo[d]chromeno[3,4- h][1,6,3]oxathiazo-nine-14,16-dicarboxylates 4 and (S)-methyl 2-(2-methoxy-2-oxoethyl)-2,3- dihydrobenzo[d]thiazole-2-carboxylates 5 were readily synthesized in a ratio 3:1 and moderated yield by multicomponent reactions of 4-hydroxycoumarin and acetylenic esters with benzothiazole without using a catalyst. Also, The GIAO/DFT approach at the B3LYP/6-31G** level of theory was used to calculate the (1)H, (15)N, (17)O and (13)C NMR chemical shifts of product 4b. These computations are performed on the basis of X-ray structural data which are collected at 120(2) K temperature. In order to take into account intermolecular hydrogen bonds and the van der Waals effects, two different sizes of clusters (two model of trimeric and pentameric clusters) have been considered. A comparison between the experimental (Exp.) and calculated (Cal.) (1)H and (13)C NMR chemical shifts may reveal that the solution contains monomer, trimer1, trimer2, and pentamer models.
authors.affiliation: Department of Chemistry, Collage of basic Science, East Tehran Branch, Islamic Azad University, PO Box 33955-163, Tehran, Iran. jahanbani.ho@gmail.com.
authors.forename: Hoorieh
authors.initials: H
authors.lastname: Djahaniani
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Fatemi
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Ektefa
authors.forename: Bita
authors.initials: B
authors.lastname: Mohtat
authors.forename: Behrouz
authors.initials: B
authors.lastname: Notash
mesh_terms: D001578:Benzopyrans / Q000138:chemical synthesis* / Q000737:chemistry; D006573:Heterocyclic Compounds, 1-Ring / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D011789:Quantum Theory; D013237:Stereoisomerism; D013829:Thiadiazines / Q000138:chemical synthesis* / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D001578:Benzopyrans; D006573:Heterocyclic Compounds, 1-Ring; D013829:Thiadiazines; C517814:oxathiane; D014867:Water; C012864:dazomet