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Twenty-two novel, variously substituted nitroazetidines were designed as both sulfonamide and urethane vinylogs possibly endowed with antimicrobial activity. The compounds under study were obtained following a general procedure recently developed, starting from 4-nitropentadienoates deriving from a common β-nitrothiophenic precursor. While being devoid of any activity against fungi and Gram-negative bacteria, most of the title compounds performed as potent antibacterial agents on Gram-positive bacteria (E. faecalis and three strains of S. aureus), with the most potent congener being the 1-(4-chlorobenzyl)-3-nitro-4-(p-tolyl)azetidine 22, which displayed potency close to that of norfloxacin, the reference antibiotic (minimum inhibitory concentration values 4 and 1–2 μg/mL, respectively). Since 22 combines a relatively efficient activity against Gram-positive bacteria and a cytotoxicity on eucharyotic cells only at 4-times higher concentrations (inhibiting concentration on 50% of the cultured eukaryotic cells: 36 ± 10 μM, MIC: 8.6 μM), it may be considered as a promising hit compound for the development of a new series of antibacterials selectively active on Gram-positive pathogens. The relatively concise synthetic route described herein, based on widely available starting materials, could feed further structure–activity relationship studies, thus allowing for the fine investigation and optimization of the toxico-pharmacological profile.

Our research groups have been involved for many years in studies aimed at identifying new active organic compounds endowed with pharmacological properties. In this work, we focused our attention on the evaluation of cardiovascular and molecular drug resistance (MDR) reverting activities of some nitrosubstituted sulphur-containing heterocycles. Firstly, we have examined the effects of 4-nitro-3-(4-methylphenyl)-3,6-dihydro-2H-thiopyran S,S-dioxide 5, and have observed no activity. Then we have extended our investigation to the 3-aryl-4-nitrobenzothiochromans S,S-dioxide 6 and 7, and have observed an interesting biological profile. Cardiovascular activities were assessed for all compounds using ex vivo studies, while the MDR reverting effect was evaluated only for selected compounds using tumor cell lines. All compounds were shown to affect cardiovascular parameters. Compound 7i exerted the most effect on negative inotropic activity, while 6d and 6f could be interesting molecules for the development of more active ABCB1 inhibitors. Both 6 and 7 represent structures of large possible biological interest, providing a scaffold for the identification of new ABCB1 inhibitors.

Herein we report a significant, valuable extension of a recently implemented pyrrole benzannulation methodology that, employing versatile nitrodienes from our lab as useful C4 building blocks, led to indole derivatives characterized by unusual patterns of substitution. The 6-nitro-7-arylindoles resulting from suitably derivatized, non-symmetric dienes are of foreseeable synthetic interest in search for new polyheterocyclic systems. As an example, pyrrolocarbazoles with a rarely reported ring fusion were synthesized with the classical Cadogan protocol. Furthermore, the proven easy reducibility of the nitro group to amine will surely open the way to further interesting elaborations.

We report herein an original protocol to the indole nucleus, which could contribute to significantly expand the synthetic access to a heterocyclic moiety of undeniable paramount importance. The protocol consists in the construction of the benzene ring onto a pyrrole (benzannulation) starting from 2,3-dinitro-1,3-butadienes. This appealing, metal-free process characterized by high atom economy and mild reaction conditions allows to synthesize indoles possessing nitro group(s) on the benzene ring: a result which cannot be likewise easily obtained by exploiting most common pathways such as functionalization of a preformed indole or heteroannulation of a suitable benzene derivative. From a mechanistic point of view, a stepwise, ionic process is suggested by the identification of a pivot dihydroindole intermediate whose interception facilitates some selectivity in the preparation of different nitroindoles.

A series of 1-[(methylsulfonyl)methyl]-2-nitro-5,6,7,8-tetrahydroindolizines and homologs were designed, prepared, and evaluated as non-sugar-type α-glucosidase inhibitors. The inhibitory activity appeared to be related to cyclo homologation with the best congeners being tetrahydroindolizines. The introduction of a methoxycarbonyl group as an additional hydrogen bond acceptor into the exocyclic methylene group was beneficial affording the most potent congener 3e (half maximal inhibitory concentration, IC50=8.0±0.1μM) which displayed 25-fold higher inhibitory activity than 1-deoxynojirimycin (2, IC50=203±9μM)-the reference compound. Kinetic analysis indicated that compound 3e is a mixed inhibitor with preference for the free enzyme over the α-glucosidase-substrate complex (Ki,free=3.6μM; Ki,bound=7.6μM). Molecular docking experiments were in agreement with kinetic results indicating reliable interactions with both the catalytic cleft and other sites. Circular dichroism spectroscopy studies suggested that the inhibition exerted by 3e may involve changes in the secondary structure of the enzyme. Considering the relatively low molecular weight of 3e together with its high fraction of sp3 hybridized carbon atoms, this nitro-substituted tetrahydroindolizine may be considered as a good starting point towards new leads in the area of α-glucosidase inhibitors.

The ring opening of 3-nitro-4-(phenylsulfonyl)thiophene with amines and proper modification of the resulting 1,3-diene enables a simple and versatile approach to N-fused pyrroles of both synthetic and biological interest through 1,6-H shift followed by 6π 1,5-electrocyclization. This protocol is effectively driven to the isolated pyrroles by an easy aromatization.

The unusual migration of a nitro group from the - to the -position of a -aryl--nitroethenyl moiety, following a nitrocyclopropane to isoxazoline N-oxide isomerization, has been studied from a mechanistic and synthetic points of view. As a result, two series of isomeric isoxazoline N-oxides could be obtained under controlled conditions. When reacted with diazomethane, a model transposed isoxazoline cleanly furnished a new, interesting pyrazolylisoxazole.

The conjugated bis(sulfonyl)nitrobutadienes 1 undergo, with primary amines, competitive MeSO2 replacement [vinylic substitution at C(1)] versus aza-Michael addition to the nitroethenyl C(3)–C(4) double bond. The latter pathway eventually leads to the trisubstituted pyrroles 2 and conditions have been optimized in order to maximize the yield of such polyfunctionalized heterocycles. Interestingly, in trifluoroethanol tetrasubstituted pyrroles 7 are also formed, thanks to a final aromatization via oxidation by ‘endogenous’ nitrite.

The base-induced cyclization of ( E )-2-aryl-1-[2-(benzylsulfonyl)phenyl]-1-nitroethenes to polysubstituted thiochroman S , S -dioxides exhibits a diastereoselectivity that can be oriented towards a selected isomer by means of appropriate adjustments of the experimental conditions. The interest of such a result also rests on the promising pharmacological activity of the products, whose structure encompasses different well-acknowledged pharmacophores. A conformational 1 H NMR investigation, backed by molecular-mechanics calculations, has also been accomplished.

(1 E ,3 Z )-1-Aryl-4-methanesulfonyl-2-nitro-1,3-butadienes ( 8 ), derived from the initial ring-opening of 3-nitrothiophene ( 5 ), have been found to undergo a facile base-induced cyclization leading to thiopyran S , S -dioxides ( 9 ), thus furnishing a further example of effective ring-enlargement from 5- to 6-membered sulfur heterocycles. Compounds 9 are obtained as single racemic mixtures in satisfactory yields; they still contain a nitrovinylic moiety, which can be exploited for further modifications targeted to new derivatives endowed with either synthetic or pharmacological potentialities e.g., in the field of L-type Ca 2+ -channel blockers.

With the goal of their exploitation for the synthesis of heterocycles, sulfides 10 and sulfones 11, derived from the initial ring-opening of 2-nitrothiophene (5) with pyrrolidine/AgNO3 in EtOH, were reacted with diazomethane. Interesting dichotomic behavior was found to yield pyrazolines 17 from 10 and isoxazolines 18 (as the main products) from 11. Intriguingly enough, in the latter case, an unexpected apparent C-C methylene insertion was also observed, leading to the homologous cyclopropanes 19 as secondary products.

Reference EPFL-ARTICLE-150326doi:10.2174/157017807781024165 URL: http://www.bentham.org/loc/contabs/loc4-4.htm#13 Record created on 2010-08-06, modified on 2017-05-12

The treatment of 3,4-dinitrothiophene with an aryl Grignard reagent results in the reduction of one nitro group accompanied by the ipso-substitution of a hydrogen atom by an ortho-phenolic group on the ring carbon adjacent to the reduced nitro group. A Claisen-type intramolecular rearrangement is proposed as the pivotal step of a rather complex mechanism, followed by proton-transfer aromatizing steps. This work shows yet another facet of the variegated reactivity of 3,4-dinitrothiophene towards nucleophiles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Within an overall ring-opening/ring-forming protocol, the (E,E)-4-methylthio-2-nitro-3-phenylsulfonyl-1-pyrrolidino-1,3-butadiene (7) [derived from the initial opening of 3-nitro-4-(phenylsulfonyl)thiophene (6) with pyrrolidine and silver nitrate in EtOH] is revealed to be an excellent precursor of nitro(phenylsulfonyl) derivatives of ring-fused aromatic (naphthalene, phenanthrene) or heteroaromatic (benzothiophene) compounds whose substitution pattern cannot be easily achieved by conventional methods. The key step is represented by a thermal electrocyclic rearrangement of (E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (9), which, thanks to proper geometric and electronic factors, occurs in unprecedentedly mild conditions and is followed by an irreversible, concerted syn β-elimination of methanesulfinic acid to aromatize the newly formed cyclohexadienic ring.

The ring opening of 3-nitro-4-(phenylsulfonyl)thiophene with amines and proper modification of the resulting 1,3-diene enables a simple and versatile approach to N-fused pyrroles of both synthetic and biological interest through 1,6-H shift followed by 6π 1,5-electrocyclization. This protocol is effectively driven to the isolated pyrroles by an easy aromatization.

The reactions between 1,2-bis(diethylamino)-2,3-dinitro-1,3-butadiene, easily obtainable by ring-opening of 3,4-dinitrothiophene with diethylamine, and arylmethylmagnesium chlorides in THF at 0°C furnished good yields of (E,E,E)-1,6-diaryl-3-nitro-1,3,5-hexatrienes. To explain the formation of the hexatrienes, a mechanism is advanced which involves, in particular, tautomerisation of the intermediate 1,6-diaryl-3,4-dinitro-2,4-hexadienes followed by base-induced elimination of nitrous acid. The electrocyclic disrotatory conversion of the hexatrienes into the corresponding 5,6-diaryl-2-nitro-1,3-cyclohexadienes was analysed by 1H NMR spectroscopy and exploited for the high-yielding synthesis of 1,2-diaryl-4-nitrobenzenes employing, as oxidants, either DDQ or iodine in the presence of cyclohexene oxide as HI scavenger.

(Z)-4-Nitrophenyl tert-butylsulfide [(Z)-4-NO2−1], upon formation of its radical anion, isomerizes to the (E)-isomer at a very fast rate of 6.3 × 106 s-1, about 103 times faster than azobenzene, while the 4-fluoro tert-butylsulfide (4-F−1) cleaves without isomerization. The particular behavior of 4-NO2−1 is related to the occurrence of a cleavage recombination mechanism, different from the usual inversion rotation mechanism. The existence of a reversible cleavage for the radical anion of 4-NO2−1 bears consequences on the mechanism of SRN1 reactions of azosulfides; the attack of the nucleophile would take place on the intermediate diazenyl radical and not on the ensuing aryl radical as previously proposed.

The reactions between 1,4-bis(diethylamino)-2,3-dinitro-1,3-butadiene (2), easily obtainable by ring-opening of 3,4-dinitrothiophene with diethylamine, and 2-substituted vinylmagnesium bromides gave good yields of the 4,5-dinitro-1,3,5,7-octatetraene derivatives 3a–e. With 1-phenylmagnesium bromide, conversely, only 3,4-dinitro-1,4-diphenyl-1,3,5-cyclooctatriene (4f) was obtained. From the unsubstituted dinitrooctatetraene 3a both the octatriene cycloisomer 4a and the valence tautomer of the latter (6a) could be isolated and characterized. The results obtained evidence an unfavourable effect of the two nitro groups on the cycloisomerization process of the octatetraene system.

1-Aryl-2-(p-tolylazo)alkenes were synthesized starting from alkyl aryl ketones in good overall yield. The employed three-step procedure involves: i) α-p-tolylhydrazonylation of ketone enolates with tert-butyl p-tolylazosulfide 1; ii) selective reduction of the carbonyl function of the obtained α-p-tolylhydrazono ketones 3 with NaBH4; iii) dehydration of the ensuing hydrazono alcohols 4 either in an Et2O/dil. H2SO4 two-phase system or in pyridine/acetic anhydride.

The reactions of arylazosulfones 1 (ArNNSO 2 Ar 1 ) with the potassium salts of ( tert -butoxycarbonyl)methyl 2 and tosylmethyl isocyanide 3 in DMSO afford 4,5-bis( tert -butoxycarbonyl)- 4 and 4-tosyl-1-arylimidazoles 5 , respectively. Yields of imidazoles 4 and 5 vary from moderate to excellent depending on the nature both of Ar in 1 and of the nucleophile ( 2 or 3 ) employed. A comparison of the results obtained with those relevant to the reactions of the same nucleophiles with nitrosobenzene in analogous experimental conditions provides useful mechanistic indications on the transformation of 1 to 4 or 5 .

In prosecution of the synthetic exploitation of nitrobutadienes deriving from the initial ring-opening of nitrothiophenes, their multifaceted behavior finds a further clear-cut example in their Michael-type acceptor reactivity toward the anions of α-oxohydrazones. Thus, depending on the starting diene, new poly-functionalized pyrazoles are obtained. Furthermore, most interestingly, in one occasion a dichotomy has been observed, depending on the nature of the Michael-type donor, leading with complete selectivity to either 5-member or 6-member N-heterocycles. The outcome encompasses motifs for both mechanistic and synthetic interest, for example, in the field of heterocycles endowed with possible pharmacological/biological activity.

The multifaceted behavior of nitrobutadienes deriving from the initial ring-opening of nitrothiophenes finds a further clear-cut example in their Michael-type acceptor reactivity towards indole. Thus, depending on the starting diene, either newly-functionalized indoles or carbazoles are produced, the latter as the result of an appealing double (intermolecular + intramolecular) Michael-type addition to a nitrovinylic moiety. The outcome encompasses motifs for both mechanistic and synthetic interest in the field of heterocycles endowed with possible pharmacological activity.

The title reaction conveniently furnishes, as the sole or main products, α-(p-tolylhydrazono)ketones or their N-methylderivatives (H+ or MeI quenching of the final mixture, respectively). Although the method fails with ketones having a secondary alkyl group bonded to the carbonyl, yields are otherwise more than satisfactory and particular interest is attached to the hydrazonylation of the methyl group in methyl ketones.

Potassium enolates of alkyl aryl ketones react selectively in DMSO with phenylazo 1a and 4 -methylphenylazo tert-butyl sulfide 1b undergoing respectively effective α-phenylation via S RN 1 and α-(4-methylphenyl)hydrazonylation via elimination-addition.

The ortho -arylation of phenols by (2-cyanoaryl)azo t -butyl (or phenyl) sulfides in S RN 1 conditions, followed by a silica-gel-catalysed lactonisation of the resulting 2-cyano-2′-hydroxybiphenyls, leads to dibenzo[ b,d ]pyran-6-ones.

Potassium enolates of alkyl aryl ketones react selectively in DMSO with phenylazo 1a and 4 -methylphenylazo tert-butyl sulfide 1b undergoing respectively effective α-phenylation via S RN 1 and α-(4-methylphenyl)hydrazonylation via elimination-addition.

The outcome of the reaction between azosulfides 1 and ketone enolates is influenced by the presence of suitable alkyl substituents on the aryl moiety of 1. The system can thus be conveniently exploited for the selective synthesis of different classes of derivatives of remarkable applicative interest, namely α-aryl ketones, α-arylhydrazono ketones, or indazoles.

The title reaction conveniently furnishes, as the sole or main products, α-(p-tolylhydrazono)ketones or their N-methylderivatives (H+ or MeI quenching of the final mixture, respectively). Although the method fails with ketones having a secondary alkyl group bonded to the carbonyl, yields are otherwise more than satisfactory and particular interest is attached to the hydrazonylation of the methyl group in methyl ketones.

The reaction between arylazo p-tolyl sulfones la-f (Ar-N=N-SO 2p-Tol) and the potassium salts of some active-methylene compounds (CH2XY: X, Y = CN, COOEt) represents an example of unprecedented behaviour of azosulfones and effectively leads, depending on the nucleophile, to either unsymmetrical ( 6–8) or symmetrical (9) tetrasubstituted ethylenes. Of particular interest is the possibility to synthesize, in high yields and mild conditions, polarysed ethylenes lArNHCX=CXY: X = Y = CN (6) or X = COOEt, Y = CN (7)] some of which are otherwise not easily accessible. A mechanism involving successive condensation processes is supported by experimental evidence.

The reactions of arylazosulfones 1 (ArNNSO 2 Ar 1 ) with the potassium salts of ( tert -butoxycarbonyl)methyl 2 and tosylmethyl isocyanide 3 in DMSO afford 4,5-bis( tert -butoxycarbonyl)- 4 and 4-tosyl-1-arylimidazoles 5 , respectively. Yields of imidazoles 4 and 5 vary from moderate to excellent depending on the nature both of Ar in 1 and of the nucleophile ( 2 or 3 ) employed. A comparison of the results obtained with those relevant to the reactions of the same nucleophiles with nitrosobenzene in analogous experimental conditions provides useful mechanistic indications on the transformation of 1 to 4 or 5 .

1-Aryl-2-(p-tolylazo)alkenes were synthesized starting from alkyl aryl ketones in good overall yield. The employed three-step procedure involves: i) α-p-tolylhydrazonylation of ketone enolates with tert-butyl p-tolylazosulfide 1; ii) selective reduction of the carbonyl function of the obtained α-p-tolylhydrazono ketones 3 with NaBH4; iii) dehydration of the ensuing hydrazono alcohols 4 either in an Et2O/dil. H2SO4 two-phase system or in pyridine/acetic anhydride.

The reaction conditions of the ring-opening processes of 3-nitrothiophene 7a and of 3-nitrobenzo[ b ]thiophene 7b with pyrrolidine and silver nitrate were optimized as well as those of the subsequent S -methylation of the ensuing silver enethiolates 8a and 8b to 4-methylthio-2-nitro-1-pyrrolidino-1,3-butadiene 9a and 1-(2-methylthiophenyl)-1-nitro-2-pyrrolidinoethylene 9b . Under such conditions 2-X-substituted 4-nitrothiophenes 7c – i consistently gave good yields of the corresponding 4-methylthio-2-nitro-1-pyrrolidino-4-X-1,3-butadienes 9c – i . The nitroenamine derivatives 9a – i were then reacted with p -tolylmagnesium bromide to furnish moderate to good yields of 4-methylthio-2-nitro-1-( p -tolyl)-4-X-1,3-butadienes 10a , c – i and 1-(2-methylthiophenyl)-1-nitro-2-( p -tolyl)ethylene 10b . Stereochemistry of the interesting building blocks 9a – i and 10a – i was assigned on the grounds of 1 H NMR data and NOE experiments.

The reactions of 1,1-bis(methylthio)-3-nitro-4-pyrrolidino-1,3-butadiene (deriving from the initial ring-opening of 2-methylthio-4-nitrothiophene with pyrrolidine and silver nitrate in EtOH) with arylmagnesium bromides result in the chemoselective replacement of the pyrrolidino group with the aryl moiety of the Grignards. The 4-aryl-1,1-bis(methylthio)-3-nitro-1,3-butadienes thus obtained are the key intermediates for the effective synthesis, through the corresponding reduction products 4-aryl-3-hydroximino-1,1-bis(methylthio)-1-butenes, of the previously unknown 3-arylmethyl-5-(methylthio)isoxazoles.

(Z)-Arylazo tert-butyl sulfides 1a-i react, in DMSO and at room temperature, with potassium acetone enolate to give good yields of 1-aryl-2-propanones via spontaneous SRN1 dark reactions, α-Phenylation of pinacolone and acetophenone enolates by 1a likewise occurs in excellent yields. In agreement with the involvement of an electron-transfer catalyzed chain process, the reaction of the 4-bromo derivative 1n with pinacolone enolate gives mainly the bis-substitution product 13. With azosulfides 1j–m the arylation pathway competes with a base-induced thiol elimination eventually leading, depending on the structure of the azosulfide, to indazoles 8 or 11 and/or to 2-oxopropanal arylhydrazones 9, 10 or 12.

1-(Methyl-p-tolyl-amino)-3-phenoxy-2-azetidinones 4-COX and 4-R substituted (COX: X=Me, Et, Ph, NMe2, NEt2, OBut; R=Me, Et, Ph) were smoothly prepared from the corresponding α-(methyl-p-tolyl)hydrazonylated ketones, amides and esters via [2+2] cycloaddition with phenoxyketene. The reaction was generally high-yielding and diastereoselective, leading to β-lactams with a cis relationship between the PhO and the COX moieties, except for R=Ph, where an opposite stereoselectivity was instead observed. The azetidinones represent interesting intermediates which couple protection at N(1) and functionalization at position 4 of the ring. Deprotection of N(1) can be easily attained by oxidative N–N cleavage with magnesium monoperoxyphthalate.

The (E)-2-aryl-1-[2-(methylthio)phenyl]-1-nitroethylenes 5 can easily be oxidized to the relevant sulfones 6 and effectively subjected to cyclization via an intramolecular Michael addition after metallation with lithium bis(trimethylsilyl)amide in THF. After quenching with ammonium chloride the 3-aryl-4-nitrothiochroman S,S-dioxides 2 are obtained as diastereomeric mixtures in good to excellent yields. Both yields and stereochemistry of the ring-closure step appear to be influenced by steric effects of the 3-aryl moiety. As sulfides 5 derive from an initial ring opening of 3-nitrobenzo[b]thiophene ( 1 ), the overall 1 to 2 process can be considered as an effective 5 to 6 ring enlargement of the sulfur heterocycle. A conformational 1H NMR and molecular-mechanics investigation on the isolated diastereomeric 2 has also been accomplished.

We report on the synthesis of novel liquid crystalline polyacetylenes derived from monosubstituted acetylene monomers. In the monomers A1OBP-Acn obtained from 3-bromo-1-propyne, the acetylenic moiety is linked through a very short spacer to a biphenyl mesogenic core. Several linear acyl groups of different length are introduced as tail groups. Most of the monomers show liquid crystalline behavior. Polymerizations are carried out in solution with typical metathesis catalysts based on Mo and W and yield polyacetylenes with fairly high molecular weight (MW), soluble in common organic solvents. Polymers PA1OBP-Acn are fully characterized in terms of molecular structure, by GPC, FT-IR, NMR and UV/VIS techniques, and of thermal and morphological behavior, by TGA, DSC, POM and X-ray diffraction experiments. THF solutions of the polymers show a quite relevant photoluminescence with a broadened maximum located around 450 nm.

By means of an iodide-catalyzed nitrocyclopropane to 4,5-dihydroisoxazoline 2-oxide isomerization, the 1,1'-dinitro-(1,1')bi(cyclopropyl)s 5, deriving from an initial ring-opening of 3,4-dinitrothiophene 1, can be stereospecifically converted into the bisnitronates 6. From these, successive N-oxide reduction (P(OMe)3/dioxane) and aromatization (DDQ/toluene) provide convenient access to the interesting 4,5,4'5'-tetrahydro(3,3')bi-isoxazolyls 7, and (3,3')bi- isoxazolyls 8, respectively.

1,4-Dialkyl- and 1,4-diaryl-2,3-bis(hydroxyimino)butanes 7, from reduction of the corresponding 1,4-disubstituted 2,3-dinitro-1,3-butadienes 2, are transformed with satisfactory yields into 3,4-disubstituted 1,2,5-oxadiazole-2-oxide 5 and 4,5-disubstituted 2-phenyl-2H-1,2,3-triazole-1-oxides 6. Dinitrobutadienes 2 are obtained from the reaction of 3,4-dinitrothiophene with diethylamine and subsequent treatment of the ensuing bis(diethylamino)butadiene 1 with Grignard reagents; thus the overall transformation represents a novel approach to 1,2,5-oxadiazole and 1,2,3-triazole systems via a ring-opening ring-closure strategy.

Treatment of variously substituted ( o -alkylaryl)azosulfides 1a-n with potassium tert -butoxide in DMSO at room temperature smoothly furnishes 1 H -indazoles 2a-n .

The outcome of the reaction between azosulfides 1 and ketone enolates is influenced by the presence of suitable alkyl substituents on the aryl moiety of 1. The system can thus be conveniently exploited for the selective synthesis of different classes of derivatives of remarkable applicative interest, namely α-aryl ketones, α-arylhydrazono ketones, or indazoles.

The ortho -arylation of phenols by (2-cyanoaryl)azo t -butyl (or phenyl) sulfides in S RN 1 conditions, followed by a silica-gel-catalysed lactonisation of the resulting 2-cyano-2′-hydroxybiphenyls, leads to dibenzo[ b,d ]pyran-6-ones.

Potassium 2,4-pentanedionate reacts with diazosulfides (E)-1 and (Z)-2 in DMSO to give 3-aryl-2,4-pentanediones 3 via an S RN 1 process. Advantages and drawbacks of such new access to 3 are reported together with relevant mechanistic implications.

Spectroelectrochemistry using a cell with a short conversion time of about 2 s and fast scan cyclic voltammetry permits us to observe the radical anions of 4-nitro- and 4-cyano-phenylazo tert -butyl sulfides and to measure the electrocatalyzed ( Z ) to ( E ) stereomutation. The rate of this fast isomerization is of the order of 10 6 s −1 . It was also possible to characterize kinetically the photostationary state obtained upon light irradiation.

C15H18N2O4S2, monoclinic, P121/c1 (No. 14), a = 8.754(3) Å, b = 12.499(2) Å, c = 15.599(3) Å, β = 95.09(2)°, V = 1700.1Å3, Z = 4, Rgt(F) = 0.049, wRref(F2) = 0.128, T = 294 K.

When Ar is a low-aromaticity homo- or heterosystem, the sulfonyl-stabilized anion of nitrobutadienes 4 (which derive from the initial ring opening of 3-nitrothiophene) undergoes a rather surprising addition onto the aromatic ring itself, thereby leading to the construction of an unusual eight-membered sulfur heterocycle condensed with the original Ar ring. The competitiveness of such a pathway with respect to the formation of the thiopyran ring (i.e., addition onto the nitrovinyl moiety) is favored at low temperatures, thus revealing its nature as a kinetically controlled process.