1.One-Pot Synthesis of 5-Amino-2,5-dihydro-1-benzoxepines: Access to Pharmacologically Active Heterocyclic Scaffolds.
Calder ED1, Sharif SA1, McGonagle FI1, Sutherland A1. J Org Chem. 2015 May 1;80(9):4683-96. doi: 10.1021/acs.joc.5b00583. Epub 2015 Apr 13.
A one-pot multibond-forming process involving a thermally mediated Overman rearrangement and a ring closing metathesis reaction of allylic trichloroacetimidates bearing a 2-allyloxyaryl group has been developed for the synthesis of 5-amino-substituted 2,5-dihydro-1-benzoxepines. Chemoselective reduction and functionalization of these compounds allowed access to a range of pharmacologically active 5-amino-2,3,4,5-tetrahydro-1-benzoxepine scaffolds.
2.Synthesis, Photochemical Properties, and Cytotoxicities of 2H-Naphtho[1,2-b]pyran and Its Photodimers.
Ota M1, Sasamori T2, Tokitoh N2, Onodera T3,4, Mizushina Y3,4, Kuramochi K1, Tsubaki K1. J Org Chem. 2015 Jun 5;80(11):5687-95. doi: 10.1021/acs.joc.5b00645. Epub 2015 May 11.
A 2H-naphtho[1,2-b]pyran, prepared by dimerization of 2-bromo-3-methyl-1,4-naphthoquinone and O-methylation, readily undergoes solid-state [2 + 2] photodimerization to give a photodimer in excellent yield and with excellent selectivity. Retro [2 + 2] cycloaddition can be achieved by irradiation of a solution of the photodimer in chloroform. Interestingly, the 2H-naphtho[1,2-b]pyran dimerizes with a skeletal rearrangement to afford 2,5-dihydro-1-benzoxepin dimers upon irradiation in methanol or via irradiation with hexamethylditin. Furthermore, treatment of the resulting dimers with triethylamine regenerates the 2H-naphtho[1,2-b]pyran monomer. Significant differences in the color, fluorescence, and cytotoxic properties of the monomer and dimers were observed.
3.4,5-Dihydro-1,2,3-oxadiazole: A Very Elusive Key Intermediate in Various Important Chemical Transformations.
Banert K1, Singh N2, Fiedler B3, Friedrich J4, Korb M5, Lang H5. Chemistry. 2015 Oct 19;21(43):15092-9. doi: 10.1002/chem.201502326. Epub 2015 Aug 10.
4,5-Dihydro-1,2,3-oxadiazoles are postulated to be key intermediates in the industrial synthesis of ketones from alkenes, in the alkylation of DNA in vivo, and in the decomposition of N-nitrosoureas; they are also a subject of great interest for theoretical chemists. In the presented report, the formation of 4,5-dihydro-1,2,3-oxadiazole and the subsequent decay into secondary products have been studied by NMR monitoring analysis. The elusive properties evading characterization have now been confirmed by (1) H, (13) C, and (15) N NMR spectroscopy, and relevant 2D experiments at very low temperatures. Our experiments with suitably substituted N-nitrosoureas using thallium(I) alkoxides as bases under apolar conditions answer important questions on the existence and the secondary products of 4,5-dihydro-1,2,3-oxadiazole.
4.Experimental and theoretical spectroscopic studies, HOMO-LUMO, NBO analyses and thione-thiol tautomerism of a new hybrid of 1,3,4-oxadiazole-thione with quinazolin-4-one.
Soliman SM1, Hagar M2, Ibid F1, El Ashry el SH3. Spectrochim Acta A Mol Biomol Spectrosc. 2015 Jun 15;145:270-9. doi: 10.1016/j.saa.2015.01.061. Epub 2015 Feb 2.
The hybrid 3-(4-chlorophenyl)-2-[(5-thioxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)methylthio]quinazolin-4(3H)-one has been synthesized and characterized using elemental analysis, FTIR and NMR spectroscopy. The thione-thiol tautomeric equilibria has been studied using both DFT/B3LYP and HF methods at different basis sets. The results of calculations showed predominance of the thione form. The molecular structure and vibrational spectra of the stable tautomer are predicted using the same level of theory. The complete assignments of the vibrational modes were performed on the basis of potential energy distribution (PED). The 6-311++G(d,p) gave the best results compared to the experimental data. The chemical shift values of the two tautomers are calculated using GIAO method. The NH proton of the thione tautomer have chemical shift value closer to the experimental data compared to the SH proton of the thiol one. The electronic transitions are predicted using the TD-DFT calculations at B3LYP/6-311++G(d,p) level of theory.