One-pot synthesis of tryptanthrin by the Dakin oxidation of indole-3-carbaldehyde

A one-pot approach to indolo[2,1-b]quinazolines from indole-3-carbaldehydes through the Dakin oxidation was developed. It was shown that the reaction proceeded through the condensation of indole-3-carbaldehydes with isatoic anhydrides, derived in situ from indole-3-carbaldehydes by the Dakin oxidation, and further oxidation/cyclization steps.     

A mild and efficient copper-catalyzed N-arylation of unprotected sulfonimidamides using boronic acids

An efficient and low cost copper catalyzed system for N-arylation of sulfonimidamides has been developed. The reaction proceeds at room temperature under base free conditions. Various N-aryl, N-heteroaryl, and N-cyclopropyl sulfonimidamides were obtained in good to excellent yields.     

Copper(II) catalyzed cross-dehydrogenative coupling of cyclic benzylic ethers with simple carbonyl compounds by Na2S2O8

Copper(II) catalyzed cross-dehydrogenative coupling of cyclic benzylic ethers with a variety of simple carbonyl compounds mediated by Na₂S₂O₈ is developed. The scope of carbonyl components is broad, including simple aldehydes as well as ketones. The use of Na₂S₂O₈ as the oxidant for the CDC reaction is attractive based on economical and environmental factors.     

Experimental and computational studies of molecules with close,non-bonded hydrogen–hydrogen contacts: common computational methods grossly overestimate some ‘through-space’ NMR scalar coupling constants

The NMR spin–spin scalar coupling constants (J_HH's) of closely contacting, but non-bonded hydrogen atoms in a series of highly strained molecules (including a new in,in-cyclophane made specifically for this study) have been examined both experimentally and computationally. The experimental J_HH's are invariably quite small (0.1–0.6 Hz), but common DFT methods with modest basis sets nearly always overestimate these values, by factors of 10–30, and even with quite large basis sets (up to cc-pVQZ) the J_HH's of two of the molecules are overestimated by a factor of 10 or more. Possible reasons for these discrepancies are discussed.     

Synthesis and characterization of 6,6″′-bis(anthracen-9-yl)-2,2′;6′,2″;6″,2″′-quaterpyridine

New bianthracene-quaterpyridine ligand 6,6″′-bis(anthracen-9-yl)-2,2′;6′,2″;6″,2″′-quaterpyridine L has been obtained in a multistep synthesis using Suzuki–Miyaura and Stille-type coupling reactions. The dianthracene ligand L has four nitrogen-donor atoms and can form different supramolecular architectures with transition metal ions. Ligand L and intermediate compounds have been characterized by spectroscopic methods and elemental analyses. 2-(Anthracen-9-yl)-6-bromopyridine and 6-(anthracen-9-yl)-6′-bromo-2,2′-bipyridine have been also characterized by X-ray crystallography.     

Metal-free cross-dehydrogenative coupling of benzimidazoles with aldehydes to N-acylbenzimidazoles

A novel and direct cross-dehydrogenative coupling (CDC) between benzimidazoles with aldehydes promoted by di-tert-butyl peroxide (DTBP) was developed. The reactions generated the corresponding N-acylbenzimidazoles in good yields under metal-free conditions. This method has broad substrate scope and high efficiency.     

Regioselective synthesis of thiophene fused sultam derivatives via iodocyclization approach and their application towards triazole linker

An efficient regioselective synthesis of 4-iodo-2,3-disubstituted-2H-thieno[3,2-e][1,2]thiazine-1,1-dioxide derivatives via iodocyclization approach using iodine under mild reaction condition described herein. This coupling–iodocyclization strategy tolerated a variety of functional groups such as alkyl, cycloalkyl, phenyl producing the six-membered heterocyclic ring selectively. The resulting 4-iodo-2,3-disubstituted-2H-thieno[3,2-e][1,2]thiazine-1,1-dioxide was coupled with a variety of boronic acids (Suzuki coupling) and activated alkenes (Heck coupling). The iodo group was utilized for Sonogashira coupling followed by efficient transformation to azido precursor, which was used for the synthesis of various thieno-sultam linked with triazole.     

Synthesis of 3-iodothiophenes via iodocyclization of (Z)-thiobutenynes

A simple synthesis of 3-iodothiophenes was demonstrated using a wide range of (Z)-thioenynes. The key step in the iodocyclofunctionalization was the selective reduction of the triple bond in (Z)-thioenynes by the addition of iodine as an electrophilic agent. The 3-iodothiophenes were obtained in good to excellent yields of 61–92%. The 3-iodothiophenes were used as substrates in Sonogashira cross-coupling reactions to obtain thiophene acetylenes.     

FeCl3·6H2O oxidation of protected resveratrol for the synthesis of tetraarylfuran-type oligostilbenes

Several 8-8-coupled tetraarylfuran-type oligostilbenes were prepared through FeCl₃·6H₂O-catalyzed regioselective oxidative couplings of protected resveratrol precursors. The global deprotection of the coupling dimers in a one-pot reaction yielded (±)-pallidol instead of the targets (±)-restrytisol B and (±)-tricuspidatol A.