An Innovative Protocol for the Synthesis of 3‐(Pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles and 9,10‐Dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles

Herein, we present an innovative, novel, and highly convenient protocol for the synthesis of 3‐(pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ) and 9,10‐dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles ( 10a , 10b , 10c , 10d , 10e ), which have been delineated from the reaction of 4‐sec‐amino‐2‐oxo‐6‐aryl‐2H‐pyran‐3‐carbonitrile ( 4a , 4b , 4c , 4d , 4e , 4f , 4g ) and 4‐sec‐amino‐2‐oxo‐5,6‐dihydro‐2H‐benzo[h]chromene‐3‐carbonitriles ( 9a , 9b , 9c , 9d , 9e ) with 2‐acetylpyridine ( 5 ) through the ring transformation reaction by using KOH/DMF system at RT. The salient feature of this procedure is to provide a transition metal‐free route for the synthesis of asymmetrical 1,3‐teraryls like 3‐(pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ) and 9,10‐dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles ( 10a , 10b , 10c , 10d , 10e ). The novelty of the reaction lies in the creation of an aromatic ring from 2H‐pyran‐2‐ones and 2H‐benzo[h]chromene‐3‐carbonitriles via two‐carbon insertion from 2‐acetylpyridine ( 5 ) used as a source of carbanion.     

Strategy to Construct Stair‐Shaped Partially Reduced Naphtho[1,2‐b]pyrano[2,3‐d]oxepines and Dinaphtho[1,2‐b,d]oxepines

A concise and efficient base‐induced synthesis of stair‐shaped, 4‐methylthio‐2‐oxo‐5,6‐dihydro‐2H‐naphtho[1,2‐b]pyran[2,3‐d]oxepine‐3‐carbonitriles ( 3 ) has been delineated by the reaction of 3,4‐dihydronaphtho[1,2‐b]oxepin‐5(2H)‐one ( 1 ) and methyl 2‐cyano‐3,3‐dimethylthioacrylate in DMSO using powdered KOH as a base at room temperature. Amination of 3 has been achieved by reaction with secondary amine in ethanol at reflux temperature to yield 4‐sec‐amino‐2‐oxo‐5,6‐dihydro‐2H‐naphtho[1,2‐b]pyran[2,3‐d]oxepine‐3‐carbonitriles ( 4 ). Reaction of 3 with aryl methyl ketone ( 5 ) in DMSO at room temperature using powdered KOH as a base produced stair‐shaped 5‐aryl‐7,8‐dihydro‐1,4‐dioxa‐2,3‐dioxodinaphtho[1,2‐b,d]oxepine ( 6 ) in good yields. However, reaction of 6‐aryl‐2H‐pyran‐2‐one‐3‐carbonitrile ( 8 ) with 3,4‐dihydronaphtho[1,2‐b]oxepin‐5(2H)‐one ( 1 ) did not give similar product, but in lieu 4‐aryl‐5,6‐dihydronaphtho[1,2‐b]oxepino[4,5‐b]pyran‐2‐ylidene)acetonitrile ( 9 ) was isolated and characterized.     

A Novel and Efficient Synthesis of 3‐[(4,5‐Dihydro‐1H‐pyrrol‐3‐yl)carbonyl]‐2H‐chromen‐2‐ones (=3‐[(4,5‐Dihydro‐1H‐pyrrol‐3‐yl)carbonyl]‐2H‐1‐benzopyran‐2‐ones)

An efficient one‐pot synthesis of 3‐[(4,5‐dihydro‐1H‐pyrrol‐3‐yl)carbonyl]‐2H‐chromen‐2‐one (=3‐[(4,5‐dihydro‐1H‐pyrrol‐3yl)carbonyl]‐2H‐1‐benzopyran‐2‐one) derivatives 4 by a four‐component reaction of a salicylaldehyde 1 , 4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one, a benzylamine 2 , and a diaroylacetylene (=1,4‐diarylbut‐2‐yne‐1,4‐dione) 3 in EtOH is reported. This new protocol has the advantages of high yields (Table), and convenient operation. The structures of these coumarin (=2H‐1‐benzopyran‐2‐one) derivatives, which are important compounds in organic chemistry, were confirmed spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this reaction is proposed (Scheme 2).     

A Facile Synthesis of Oxoindenothiazine and Dioxospiro(indene‐2,4′‐thiazine) Derivatives from (Substituted ethylidene)hydrazinecarbothioamides

(E)‐2‐[2‐(1‐Substituted ethylidene)hydrazinyl]‐5‐oxo‐9b‐hydroxy‐5,9b‐dihydroindeno[1,2‐d][1,3]‐thiazine‐4‐carbonitriles and (E)‐5‐oxo‐[(E)‐(1‐substituted ethylidene)hydrazinyl]‐2,5‐dihydroindeno[1,2‐d][1,3]thiazine‐4‐carbonitriles have been obtained from the reaction of 2‐(substituted ethylidene)hydrazinecarbothioamides with 2‐(1,3‐dioxo‐2,3‐dihydro‐1H‐inden‐2‐ylidene)propanedinitrile ( 1 ) in ethyl acetate solution. However, (Z)‐6′‐amino‐1,3‐dioxo‐3′‐substituted‐2′‐[(E)‐(1‐phenylethylidene)hydrazono]‐1,2′,3,3′‐tetrahydrospiro(indene‐2,4′‐[1,3]thiazine)‐5′‐carbonitriles were observed during the reaction of N‐substituted‐2‐(1‐phenylethylidene)hydrazinecarbothioamides with ( 1 ). The structure assignment of products has been confirmed on the basis of ¹H‐, ¹³C‐NMR, and mass spectrometry, as well as theoretical calculations.     

A Stereoselective Aldol Approach for the Total Syntheses of Two 6‐Alkylated 2H‐Pyran‐2‐ones

A simple and highly efficient stereoselective total synthesis of the 6‐alkylated pyranones (6R)‐6‐[(1E,4R,6R)‐4,6‐dihydroxy‐10‐phenyldec‐1‐en‐1‐yl]‐5,6‐dihydro‐2H‐pyran‐2‐one ( 1 ) and (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one ( 2 ) was developed using Crimmins' aldol reaction, SmI₂ reduction, Grubbs‐II‐catalyzed olefin cross‐metathesis, and Still's modified Horner? Wadsworth? Emmons reaction.     

1H, 13C and 15N NMR spectroscopic characterization of unexpected degradation products of the nifedipine analogue bis(2‐cyanoethyl) 2,6‐dimethyl‐4‐(2‐nitrophenyl)‐1,4‐dihydro‐3,5‐pyridinedicarboxylate

In the course of saponification experiments with bis(2‐cyanoethyl) 2,6‐dimethyl‐4‐(2‐nitrophenyl)‐1,4‐dihydro‐3,5‐pyridinedicarboxylate ( 1 ), an analogue of the calcium channel blocker nifedipine, three unexpected degradation products were isolated. The compounds were identified as 3‐(2‐acetamido‐1‐carboxy‐1‐propenyl)‐1‐hydroxy‐2‐indolecarboxylic acid ( 3 ), 9‐hydroxy‐1,3‐dimethyl‐β‐carboline‐4‐carboxylic acid ( 4 ) and 6‐hydroxy‐2,4‐dimethyl‐5‐oxo‐5,6‐dihydrobenzo[c][2,7]naphthyridine‐1‐carboxylic acid ( 6 ). The structures of these compounds were deduced from one‐ and two‐dimensional ¹H, ¹³C and natural abundance ¹⁵N NMR experiments (¹H,¹H‐COSY, gs‐HSQC, gs‐HMBC, ¹⁵N gs‐HMBC), and corroborated by comparison of their NMR data with the respective data for structurally similar compounds. Copyright © 2002 John Wiley & Sons, Ltd.     

Reaction of cyclic imidates with α,β‐unsaturated esters: Synthesis of new pyrrolo[2,1‐b]‐1,3‐oxazine and pyrido[2,1‐b]‐1,3‐oxazine derivatives

The cycloaddition reaction of cyclic imidates, 2‐benzyl‐5,6‐dihydro‐4H‐1,3‐oxazines 1a , 1b , 1c , 1d , 1e , 1f , with dimethyl acetylenedicarboxylate 2 , trimethyl ethylenetricarboxylate 4 , or dimethyl 2‐(methoxymethylene)malonate 6 afforded new fused heterocyclic compounds, such as methyl (6‐oxo‐3,4‐dihydro‐2H‐pyrrolo[2,1‐b]‐1,3‐oxazin‐7‐ylidene)acetates 3a , 3b , 3c , 3d , 3e , 3f (71–79%), dimethyl 2‐(6‐oxo‐3,4,6,7‐tetrahydro‐2H‐pyrrolo[2,1‐b]‐1,3‐oxazin‐7‐yl)malonates 5b , 5c , 5d , 5e , 5f (43–71%), or methyl 6‐oxo‐3,4‐dihydro‐2H,6H‐pyrido[2,1‐b]‐1,3‐oxazine‐7‐carboxylates 7a , 7b , 7c , 7d , 7e , 7f (32–59%), respectively. In these reactions, 1a , 1b , 1c , 1d , 1e , 1f (cyclic imidates, iminoethers) functioned as their N,C‐tautomers (enaminoethers) 2 to α,β‐unsaturated esters 2 , 4, and 6 to give annulation products 3 , 5 , and 7 following to the elimination of methanol, respectively. J. Heterocyclic Chem., (2011).     

An Efficient Synthesis of 3‐(3‐benzyl‐2‐(phenylimino)‐2,3‐dihydrothiazol‐4‐yl)‐6‐methyl‐4‐(2‐oxo‐2‐phenylethoxy)‐3,4‐dihydro‐2H‐pyran‐2‐one Derivatives via Multi‐Component Approach

An easy, highly efficient and a new convenient one‐pot, two‐step approach to the synthesis of 3‐(3‐benzyl‐2‐(phenylimino)‐2,3‐dihydrothiazol‐4‐yl)‐6‐methyl‐4‐(2‐oxo‐2‐phenylethoxy)‐3,4‐dihydro‐2H‐pyran‐2‐one is described. These compounds were synthesized from 3‐(3‐benzyl‐2‐(phenylimino)‐2,3‐dihydrothiazol‐4‐yl)‐4‐hydroxy‐6‐methyl‐3,4‐dihydro‐2H‐pyran‐2‐one and α‐bromoketones in good yields. The compounds 4 were synthesized by a multi‐component reaction between 1 , 2 , and 3 and the prominent features of this protocol are mild reaction conditions, operation simplicity, and good to high yields of products.     

A Convenient Synthetic Route of Diethyl (4‐Oxo‐chromeno[2,3‐d]pyrimidin‐2(5)‐yl)phosphonates

Novel diethyl (4‐oxo‐3,4‐dihydro‐2H‐chromeno[2,3‐d]pyrimidin‐2‐yl)phosphonate as two enantiomers and diethyl (4‐oxo‐1,5‐dihydro‐4H‐chromeno[2,3‐d]pyrimidin‐5‐yl) phosphonate were obtained in easy procedure via reaction of 2‐imino‐2H‐chromene‐3‐carboxamide, dimethylformamide dimethyl‐acetal, and diethyl phosphite in a simple one pot. Possible reaction mechanisms were proposed. The structures of the obtained products were confirmed by elemental analyses and spectral tools.     

One‐Pot ‘On‐solvent’ Multicomponent Protocol for the Synthesis of Medicinally Relevant 4H‐Pyrano[3,2‐c]quinoline Scaffold

‘One‐pot’ AcONa‐catalyzed transformation of salicylaldehydes, malononitrile and 4‐hydroxy‐1‐methylquinolin‐2(1H)‐one in the presence of a minimal quantity of EtOH results in fast (3 min) and efficient formation of unknown 2‐amino‐4‐(2‐hydroxyaryl)‐6‐methyl‐5‐oxo‐5,6‐dihydro‐4H‐pyrano[3,2‐c]quinoline‐3‐carbonitriles in 85–98% yields, which are potential pharmaceutical agents for treating disorders responsive to the induction of apoptosis, antiproliferation, or vascular disruption. This efficient ‘on‐solvent’ approach to the 4H‐pyrano[3,2‐c]quinoline scaffold represents a novel synthetic concept for multicomponent reaction (MCR) strategy and allows to combine the synthetic virtues of conventional MCR with ecological benefits and convenience of facile ‘on‐solvent’ procedure.     

A convenient route to pyridones,pyrazolo[2,3‐a]pyrimidines and pyrazolo[5,1‐c]triazines incorporating antipyrine moiety

Condensation of 4‐aminoantipyrine with ethyl acetoacetate, ethyl benzoylacetate, and ethyl cyanoacetate furnished the corresponding ethyl 3‐(1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐3H‐pyrazol‐4‐yl)aminoacrylate and 2‐cyano‐N‐[(1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐3H‐pyrazol‐4‐yl)]acetamide derivatives. The aminoacrylates derivatives react with acetonitrile and sodium hydride to give 2‐amino‐6‐methyl‐1‐(1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐3H‐pyrazol‐4‐yl)‐4‐pyridone. Reaction of the cyanoacetamide derivative with dimethylformamide‐dimethylacetal (DMF‐DMA) afforded 2‐cyano‐N‐[1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐pyrazol‐4‐yl]‐2‐(N,N‐dimethylamino)methylene acetamide in high yield. Treatment of the latter with 5‐aminopyrazole derivatives afforded the corresponding pyrazolo[2,3‐a]pyrimidines. 2‐cyano‐N‐[(1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐3H‐pyrazol‐4‐yl)]acetamide also reacts with heterocyclic diazonium salts to give the corresponding pyrazolo[5,1‐c]‐1,2,4‐triazine derivatives. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:508–514, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20046     

Reaction of 2,3‐Dichloro‐1,4‐Naphthoquinone with 1‐Phenylbiguanide and 2‐Guanidinebenzimidazole

When 2,3‐dichloro‐1,4‐naphthoquinone (DCHNQ) ( 1 ) is allowed to react with 1‐phenylbiguanide (PBG) ( 2 ), 4‐chloro‐2,5‐dihydro‐2,5‐dioxonaphtho[1,2‐d]imidazole‐3‐carboxylic acid phenyl amide ( 4 ), 6‐chloro‐8‐phenylamino‐9H‐7,9,11‐triaza‐cyclohepta[a]naphthalene‐5,10‐dione ( 5 ) and 4‐dimethyl‐amino‐5,10‐dioxo‐2‐phenylimino‐5,10‐dihydro‐2H‐benzo[g]quinazoline‐1‐carboxylic acid amide ( 6 ) were obtained. While on reacting 1 with 2‐guanidinebenzimidazole (GBI) ( 3 ) the products are 3‐(1H‐benzoimidazol‐2‐yl)‐4‐chloro‐3H‐naphtho[1,2‐d]imidazole‐2,5‐dione ( 7 ) and 3‐[3‐(1H‐benzoimidazol‐2‐yl)‐ureido]‐1,4‐dioxo‐1,4‐dihydronaphthalene‐2‐carboxylic acid dimethylamide ( 8 ).     

New synthesis and reactivity of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with binucleophilic amines

3‐(Bromoacetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one was synthesized by the reaction of dehydroacetic acid (DHAA) with bromine in glacial acetic acid. Novel heterocyclic products were synthesized from the reaction of bromo‐DHAA with alkanediamines, phenylhydrazines, ortho‐phenylenediamines, and ortho‐aminobenzenethiol. The obtained new products 3‐(2‐N‐substituted‐acetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐ones, 4‐hydroxy‐3‐[1‐hydroxy‐2‐(2‐phenylhydrazinyl)vinyl]‐6‐methyl‐2H‐pyran‐2‐one, 1‐(2,4‐dinitrophenyl)‐7‐methyl‐2,3‐dihydro‐1H‐pyrano[4,3‐c]pyridazine‐4,5‐dione, 3‐(3,4‐dihydroquinoxalin‐2‐yl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one/3‐(3,4‐dihydroquinoxalin‐2‐yl)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione, 6‐methyl‐3‐(3,4‐dihydroquinoxalin‐2‐yl)‐2H‐pyran‐2,4(3H)‐dione, and (E)‐3‐(2H‐benzo[b][1,4]thiazin‐3(4H)‐ylidene)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione were fully characterized by IR, ¹H and ¹³C NMR, and mass spectra. J. Heterocyclic Chem., 2011.     

A convenient one‐pot synthesis of new 3‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐ones

Anhydrous zinc bromide catalysed reactions of arylidine‐3‐acetyl coumarins ( 1a‐c ) and 5,6‐benzoanalogs of arylidine 3‐acetyl coumarins ( 4a,4b ) with 1,3‐cyclohexanedione gives ‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2yl)‐2H‐chromen‐2‐ones ( 3a, 3c ) and 5,6‐benzoanalogs of 3‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2yl)‐2H‐chromen‐2‐one ( 5a,5b ). Under similar conditions arylidine‐3‐acetylcoumarins ( 1a, 1b,1d, 1e, 1f ) and 5,6‐benzoanalog of arylidine 3‐acetyl coumarin ( 4b ) react with 5,5‐dimethyl‐1,3‐cyclohexanedione (dimedone) yielding 3‐(4‐aryl‐7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐ones ( 3d‐3h ) and the 5,6‐benzoanalog of 3.(4‐aryl‐7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐one ( 5c ).     

The Stereoselective Total Synthesis of (6S)‐5,6‐Dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one via Prins Cyclization

The stereoselective total synthesis of an antiproliferative and antifungal α‐pyrone natural product (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one is described. The key steps involved are the Prins cyclization, Mitsunobu reaction, and ring‐closing metathesis reaction.     

Regioselective Synthesis of Amino Substituted Indazolo[2,1‐b]phthalazine‐triones and Pyrazolo[1,2‐b]phthalazine‐2‐carbonitriles Catalyzed by 2‐1′‐Methylimidazolium‐3‐yl‐1‐ethyl Sulfate

The regioselective reactions of luminol with 1,3‐cyclohexanedione (or malononitrile) and aromatic aldehydes catalyzed by 2‐1′‐methylimidazolium‐3‐yl‐1‐ethyl sulfate were developed to synthesize 7‐amino‐3,4‐dihydro‐2H‐indazolo[2,1‐b]phthalazine‐1,6,11(13H)‐triones and 3,9‐diamino‐5,10‐dihydro‐5,10‐dioxo‐1H‐pyrazolo[1,2‐b]phthalazine‐2‐carbonitriles in good to excellent yields in short times.     

Enantioselective Synthesis of the Natural Product (S)‐Rugulactone

A simple and efficient enantioselective synthesis of (6S)‐5,6‐dihydro‐6‐[(2E)‐4‐oxo‐6‐phenylhex‐2‐en‐1‐yl]‐2H‐pyran‐2‐one (=(S)‐rugulactone) has been accomplished. The synthesis started from commercially available propane‐1,3‐diol and ethyl 3‐phenylpropanoate and involve the Horner? Wadsworth? Emmons (HWE) and Still's modified HWE olefinations, and Sharpless asymmetric epoxidation.     

New Approaches to the Synthesis of 4‐(2‐Aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones and 3‐Ureidoindoles and a Study of Their Interconversion

3‐Alkyl/aryl‐3‐ureido‐1H,3H‐quinoline‐2,4‐diones ( 2 ) and 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones ( 3 ) react in boiling concentrated HCl to give 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones ( 6 ). The same compounds were prepared by the same procedure from 2‐alkyl/aryl‐3‐ureido‐1H‐indoles ( 4 ), which were obtained from the reaction of 3‐alkyl/aryl‐3‐aminoquinoline‐2,4(1H,3H)‐diones ( 1 ) with 1,3‐diphenylurea or by the transformation of 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones ( 3 ) and 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones ( 6 ) in boiling AcOH. The latter were converted into 1,3‐bis[2‐(2‐oxo‐2,3‐dihydro‐1H‐imidazol‐4‐yl)phenyl]ureas ( 5 ) by treatment with triphosgene. All compounds were characterized by ¹H‐ and ¹³C‐NMR and IR spectroscopy, as well as atmospheric pressure chemical‐ionisation mass spectra.     

A structural study of 4‐aminoantipyrine and six of its Schiff base derivatives

Six derivatives of 4‐amino‐1,5‐dimethyl‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐3‐one (4‐aminoantipyrine), C₁₁H₁₃N₃O, (I), have been synthesized and structurally characterized to investigate the changes in the observed hydrogen‐bonding motifs compared to the original 4‐aminoantipyrine. The derivatives were synthesized from the reactions of 4‐aminoantipyrine with various aldehyde‐, ketone‐ and ester‐containing molecules, producing (Z)‐methyl 3‐[(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)amino]but‐2‐enoate, C₁₆H₁₉N₃O₃, (II), (Z)‐ethyl 3‐[(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)amino]but‐2‐enoate, C₁₇H₂₁N₃O₃, (III), ethyl 2‐[(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)amino]cyclohex‐1‐enecarboxylate, C₂₀H₂₅N₃O₃, (IV), (Z)‐ethyl 3‐[(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)amino]‐3‐phenylacrylate, C₂₂H₂₃N₃O₃, (V), 2‐cyano‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamide, C₁₄H₁₄N₄O₂, (VI), and (E)‐methyl 4‐{[(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)amino]methyl}benzoate, C₂₀H₁₉N₃O₃, (VII). The asymmetric units of all these compounds have one molecule on a general position. The hydrogen bonding in (I) forms chains of molecules via intermolecular N—H...O hydrogen bonds around a crystallographic sixfold screw axis. In contrast, the formation of enamines for all derived compounds except (VII) favours the formation of a six‐membered intramolecular N—H...O hydrogen‐bonded ring in (II)–(V) and an intermolecular N—H...O hydrogen bond in (VI), whereas there is an intramolecular C—H...O hydrogen bond in the structure of imine (VII). All the reported compounds, except for (II), feature π–π interactions, while C—H...π interactions are observed in (II), C—H...O interactions are observed in (I), (III), (V) and (VI), and a C—O...π interaction is observed in (II).     

A Convenient Synthesis of 2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]‐, ‐[2,3‐c]‐, or ‐[3,2‐c]pyridin‐4‐ones by the Reaction of the Corresponding 1‐(Chloropyridinyl)alk‐2‐en‐1‐ones with NaSH

2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]pyridin‐4‐ones 4 were prepared by a three‐step sequence from commercially available 2‐chloropyridine ( 1 ). Thus, successive treatment of 1 with ⁱPr₂NLi (LDA) and α,β‐unsaturated aldehydes gave 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ols 2 , which were oxidized with MnO₂ to 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ones 3 . The reactions of 3 with NaSH?n H₂O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3‐dihydro‐4H‐thiopyrano[2,3‐c]pyridin‐4‐ones 8 and 2,3‐dihydro‐4H‐thiopyrano[3,2‐c]pyridin‐4‐ones 12 were obtained starting from 3‐chloropyridine ( 5 ) and 4‐chloropyridine ( 9 ), respectively.