Synthesis of 2,4‐difuryl‐4H‐3,1‐benzothiazines via a furan ring migration reaction

A new simple synthetic approach to 2,4‐difuryl‐4H‐3,1‐benzothiazines from 2‐isothiocyanoaryldifuryl‐methanes in the presence of acidic catalyst is described. This rearrangement is a new example of furan ring migration reaction resulting from intramolecular attack with electrophilic carbon.     

A revised synthetic scheme of 6,6′‐dibromoindirubin

The synthetic scheme of 6,6′‐dibromoindirubin ( 2 ) was investigated in detail. The reaction of 6‐fluoro‐3‐acetoxyindole ( 7 ) with isatin ( 8 ) in methanol with Na₂CO₃ produced 6′‐fluoroindirubin in moderate yields. Its structure determination was mainly undertaken using ¹H NMR spectroscopy. On the basis of this result, the synthetic scheme of 2 reported by Cooksey was revised.     

Convenient synthesis of c2‐symmetric diazepinium salts derived from 1,1′‐binaphthyl‐2,2′‐diamine

New C₂‐symmetric atropisomeric diazepinium salts were prepared utilizing Vilsmeier‐Haack activation of corresponding formamide precursors by phosgene solution in toluene. The structures of these substances were verified by X‐ray diffraction.     

Synthesis of 2,2′‐bipyridyl‐type compounds via the suzuki‐miyaura cross‐coupling reaction

2,2′‐Bipyridyl‐type compounds may be prepared by Suzuki‐Miyaura coupling of a 2‐pyridylboronic ester with 2‐haloazines and ‐azoles. Ten examples are presented with yields of 47 to 84%. Both arylbromides and arylchlorides undergo the coupling, but the reaction is sensitive to ring substitution adjacent to the halogen.     

Synthesis and stereochemistry of 3‐acetyl‐5‐aminospiro[1,3,4‐thiadiazoline‐2,4′‐thioflavans]

Under acetylating conditions racemic thioflavanone thiosemicarbazones cyclize into racemic 3‐acetyl‐spiro[1,3,4‐thiadiazoline‐2,4′‐thioflavans] and a racemic 3‐acetylspiro[1,3,4‐oxadiazoline‐2,4′‐thioflavan] with trans O(1) or S(1) and Ph(2′_eq). Hindered rotation of the endocyclic N(3) acetyl group spirothia‐diazolines caused the formation of isomers separable by HPLC. X‐ray diffraction analyses, ¹H‐, ¹³C‐, and ¹⁵N NMR measurements as well as MOPAC QM calculations were performed to reveal the structures of these isomers.     

An efficient synthesis of 5‐benzoyloxazolines by regio‐ and stereo‐controlled reaction of N‐substituted 2‐benzoylaziridines under microwave irradiation

Several N‐acyl‐2‐benzoylaziridines were prepared conveniently in good to high yields (71‐93%) and used in the preparation of 5‐benzoyloxazolines (76‐91%) by a regio‐ and stereo‐controlled reaction in the presence of Nal as an efficient catalyst under microwave irradiation in short reaction times (5‐10 mins). The structure of the regioisomeric product was confirmed by X‐ray analysis.     

Reactions of 4‐dimethylamino‐3‐quinolinyl sulfides with nitrating mixture and transamination of 4‐dimethylamino‐3‐methylsulfinyl‐6‐nitroquinoline

4‐Amino‐3‐quinolinyl sulfides 4d‐e and 7a‐c were prepared by amination of 4‐chloro‐3‐quinolinyl sulfides 4c or 1c , respectively, in methanol (140‐160 °C) or in boiling phenol with yields up to 95 %. Reaction of 4‐dimethylamino‐3‐quinolinyl sulfides 7c and 4e with nitrating mixture proceeded simultanously as oxidation of the methylthio group to the methylsulfinyl one and as C6‐nitration to form 6‐nitro‐β‐quinolinyl sulfoxides 9c or 10b , respectively. 4‐Dimethylamino‐3‐methylsulfinyl‐6‐nitroquinoline 9c underwent acid catalysed transamination when reacting with primary aliphatic amines and ammonia.     

Photodegradation of 2‐mercaptobenzothiazole disulfide and related benzothiazoles

The photodegradation of 2‐mercaptobenzothiazole disulfide, 2‐mercaptobenzothiazole and benzothia‐zole was investigated. Benzothiazole was found to undergo photodimerization into 2,2′‐bibenzothiazole, and in the presence of oxygen to give two additional photoproducts ‐ 2‐hydroxybenzothiazole and 2‐methylbenzothiazole. The major degradation products of 2‐mercaptobenzothiazole are benzothiazole and 2‐benzothiazolesulfonic acid, with 2,2′‐thiobisbenzothiazole and 2‐mercaptobenzothiazole disulfide as the minor degradation products. Direct photolysis of 2‐mercaptobenzothiazole disulfide gave 2‐mercapto‐benzothiazole and in acetonitrile 2‐thiocyanatobenzothiazole was also detected. A mechanism is proposed to rationalize the formation of photodegradation products.     

Michael addition of dimedone with α,β‐unsaturated ketones: Synthesis of quinoline and chromene derivatives

A series of quinoline and chromene derivatives has been synthesized by Michael addition of dimedone 1 with 2‐aroyl‐3‐arylacrylonitrile 2 and study of absorption and fluorescence maxima of quinolines.     

Regioselective synthesis of 4‐aryloxymethylene‐2,3,5‐trihydrothiopyrano[3,2‐b]indoles by the thio‐claisen rearrangement of 3‐(4′‐aryloxybut‐2′‐ynylthio)indoles

A number of new 4‐aryloxymethylene‐2,3,5‐trihydrothiopyrano[3,2‐b]indoles are regioselectively synthesized in 78‐84% yield by the thio‐Claisen rearrangement of 3‐(4′‐aryloxybut‐2′‐ynylthio)indoles. The endocyclic double bonded products are isolated by introducing electron withdrawing acetyl group at the indole nitrogen and also can be converted to the corresponding exocyclic isomers by deacetylation and subsequent heating.     

Chemical properties of 4,5‐di(ethoxycarbonyl)‐1,3‐dioxolan‐2‐yl (DECDO) as a hydroxyl protecting group of the 2′‐hydroxyl function in ribonucleosides

We describe basic chemical properties of 4,5‐di(ethoxycarbonyl)‐1,3‐dioxolan‐2‐yl (DECDO) in view of its use as a protecting group for the 2′‐hydroxyl function of ribonucleosides. The DECDO group is found to be compatible with the DMTr strategy for the currently‐used oligonucleotide synthesis. Post‐synthetic treatment with ammonia results in the conversion of this protecting group into the 4,5‐dicarbamoyl‐1,3‐dioxolan‐2‐yl (DCBDO) group which is unexpectedly more stable in aqueous acidic solution.     

An efficient and green synthesis of 3,3′‐benzylidenebis (4‐hydroxy‐6‐methylpyridin‐2(1H)‐one) derivatives through multi‐component reaction in ionic liquid

A series of new 3,3′‐benzylidenebis(4‐hydroxy‐6‐methylpyridin‐2(1H)‐one) derivatives were synthesized via a three‐component reaction of an aldehyde, an aniline or ammonium acetate and 6‐methyl‐4‐hydroxypyran‐2‐one in ionic liquid. These heterocyclic compounds produced could be conveniently separated from the reaction mixture without any volatile organic solvents, and the ionic liquid could be readily reused without efficiency loss after simple treatment.     

Synthetic and spectroscopic studies of some new 2‐[1‐aryl‐4{4‐methoxyphenyl}‐6‐thioxo‐1,6‐dihydro‐1,3,5‐triazinyl]amino/hydrazonothiazolidin‐4‐ones

A series of 4‐thiazolidinones having triazinethione moieties have been synthesized by the systematic chemical modification of S‐benzylmercapto‐1‐aryl‐4‐(4‐methoxyphenyl)‐1,6‐dihydro‐1,3,5‐triazine‐6‐thione.     

Green and high efficient synthesis of triaza‐benzo[b]fluoren‐6‐one derivatives in water under microwave irradiation

Triaza‐benzo[b]fluoren‐6‐one derivatives were synthesized via the three‐component reaction of aldehyde, cyclohexane‐1,3‐dione compound and 2‐aminobenzimidazole in water under microwave irradiation. The new protocol has the advantages of excellent yield, low cost, reduced environment impact, wide scope and convenient procedure.