A sequential construction of C-C, C-O, C═N, and C═O bonds from alkenes leading to the direct synthesis of isoxazolines in the presence of tert-butyl nitrite, quinoline, and the Sc(OTf) catalyst in DCE at 80 °C has been accomplished. An unprecedented three consecutive C-H functionalizations of two styrenes are involved in this isoxazoline synthesis. In this radical-mediated reaction, one-half of the aryl alkene is converted into an intermediate 2-nitroketone, which serves as a 1,3-dipolarophile and undergoes cycloaddition with the other half of the unreacted aromatic terminal alkene. The use of an alkyne in lieu of an alkene leads to the formation of isoxazole under identical reaction conditions.

tert-Butyl nitrite serves the dual role of an oxidant as well as a N1 synthon in a multicomponent reaction involving quinolines, isoquinolines, and styrenes. Herein, two sp C-H functionalizations of styrenes and one sp C-H functionalization of quinolines and isoquinolines lead to the formation of fused quinolines and isoquinolines via three sequential C-N bond formations.

One of the cyano group of γ‐keto malononitrile gets hydrolyzed selectively to an amide in the presence of copper(II) acetate monohydrate. The in situ generated amide undergo an intramolecular dehydrative cyclization to a 1,2‐dihydropyridone intermediate. Further annulation of the 1,2‐dihydropyridone with an internal alkyne in the same pot produce a fused isoquinolone, 4‐oxo‐2,6,7‐triaryl‐4H‐pyrido[2,1‐a]isoquinoline‐3‐carbonitrile. This one‐pot process is associated with the formation of one C−C, two C−N, two C=C and a C=O bonds. The final synthesis is a four‐step process consisting of selective hydrolysis of a cyano group to an amide, dehydrative cyclization of the amide to a cyclic amide, aromatization of the cyclic amide (2‐oxo‐1,2,3,4‐tetrahydropyridine moiety) to a 2‐oxo‐1,2‐dihydropyridine and finally, the C−H/N−H annulation with an alkyne. Density functional theory calculation reveals that the highest occupied molecular orbital (HOMO) is localized at the central core extending to the nitrile group and a negligible contribution from the two phenyl rings of the diphenylacetylene. On the other hand, the lowest unoccupied molecular orbital (LUMO) is also localized at the identical central core and extended up to the other phenyl ring. The calculated ΔE(LUMO‐HOMO) is in the range of 2.88 to 3.45 eV and the compounds display emission in the green region (502–560) nm and absorption (λmax) in the range of (454–490) nm. Therefore, these molecules may find application in bio‐imaging, theranostics and various applications in material science.magnified image

A base-promoted synthesis of quinoline-4(1H)-thiones has been accomplished from the in situ generated o-alkynylthiourea, obtained by reacting o-alkynylanilines with aroyl/acyl isothiocyanates. A 6-exo-dig S-cyclization of the in situ generated thiourea is followed by a rearrangement to give quinoline-4(1H)-thiones.

tert-Butyl nitrite (TBN) mediated synthesis of 3-aryl-1,2,4-oxadiazol-5­(4H)-ones has been accomplished using terminal aryl alkenes via a biradical reaction intermediate. Three consecutive sp2 C–H bond functionalizations of styrenes afforded 3-phenyl-1,2,4-oxadiazol-5­(4H)-ones via the formation of new CN, CO, C–O, and two C–N bonds. Both of the N atoms originate from TBN, while the carbonyl oxygen is from the water (moisture) the other oxygen from the NO part of the TBN.