Über Umlagerungen bei der Cyclialkylierung von Arylpentanolen zu 2,3‐Dihydro‐1H‐inden‐Derivaten, 2. Mitteilung

On Rearrangements by Cyclialkylations of Arylpentanols to 2,3‐Dihydro‐1 H ‐indene Derivatives. Part 2. An Unexpected Rearrangement by the Acid‐Catalyzed Cyclialkylation of 2,4‐Dimethyl‐2‐phenylpentan‐3‐ol under Formation of trans ‐2,3‐Dihydro‐1,1,2,3‐tetramethyl‐1 H ‐indene The acid catalyzed‐cyclialkylation of 4‐(2‐chloro‐phenyl)‐2,4‐dimethylpentan‐2‐ol ( 1 ) gave two products: 4‐chloro‐2,3‐dihydro‐1,1,3,3‐tetramethyl‐1H‐indene ( 2 ) and also trans‐4‐chloro‐2,3‐dihydro‐1,1,2,3‐tetramethyl‐1H‐indene ( 3 ). A mechanism was proposed in Part 1 (cf. Scheme 1) for this unexpected rearrangement. This mechanism would mainly be supported by the result of the cyclialkylation of 2,4‐dimethyl‐2‐phenylpentan‐3‐ol ( 4 ), which, with respect to the similarity of ion II in Scheme 1 and ion V in Scheme 2, should give only product 5 . This was indeed the experimental result of this cyclialkylation. But the result of the cyclialkylation of 1,1,1,2′,2′,2′‐hexadeuterated isomer [²H₆]‐ 4 of 4 (cf. Scheme 3) requires a different mechanism as for the cyclialkylation of 1 . Such a mechanism is proposed in Schemes 5 and 6. It gives a satisfactory explanation of the experimental results and is supported by the result of the cyclialkylation of 2,4‐dimethyl‐3‐phenylpentan‐3‐ol ( 9 ; Scheme 7). The alternative migration of a Ph or of an i‐Pr group (cf. Scheme 6) is under further investigation.     

Über Umlagerungen bei der Cyclialkylierung von Arylpentanolen zu 2,3‐Dihydro‐1H‐inden‐Derivaten, 1. Mitteilung

On Rearrangements by Cyclialkylations of Arylpentanols to 2,3‐Dihydro‐1 H ‐indene Derivatives. Part 1. An Unexpected Rearrangement by the Acid‐Catalyzed Cyclialkylation of 4‐(2‐Chlorophenyl)‐2,4‐dimethyl pentan‐2‐ol under Formation of trans ‐4‐Chloro‐2,3‐dihydro‐1,1,2,3‐tetramethyl‐1 H ‐indene The acid‐catalyzed cyclialkylation of 2,4‐dimethyl‐4‐phenylpentan‐2‐ol led exclusively to the expected product, 2,3‐dihydro‐1,1,3,3‐tetramethyl‐1H‐indene. However, analogous cyclialkylation of 4‐(2‐chlorophenyl)‐2,4‐dimethylpentan‐2‐ol ( 1 ) gave a ca. 1 : 1 mixture of 4‐chloro‐2,3‐dihydro‐1,1,3,3‐tetramethyl‐1H‐indene ( 2 ) and of trans‐4‐chloro‐2,3‐dihydro‐1,1,2,3‐tetramethyl‐1H‐indene ( 3 ; Scheme 1). The specific action of the Cl substituent is investigated and a mechanism for this unexpected frame‐work transposition proposed.     

Über Umlagerungen bei der Cyclialkylierung von Arylpentanolen zu 2,3‐Dihydro‐1H‐inden‐Derivaten, 3. Mitteilung

On Rearrangements by Cyclialkylations of Arylpentanols to 2,3‐Dihydro‐1 H ‐indene Derivatives. Part 3. The Acid‐Catalyzed Cyclialkylation of 3,4‐Dimethyl‐ and 3‐([ ² H ₃ ]Methyl)‐4‐methyl‐3‐phenylpentan‐2‐ol The cyclialkylation of 2‐([²H₃]methyl)‐4‐methyl‐4‐phenyl[1,1,1‐²H₃]pentan‐3‐ol ( 4 ) yielded a 1 : 1 mixture of 1,1‐di([²H₃]methyl)‐2,3‐dimethyl‐1H‐indene ( 5 ) and of 2,3‐dihydro‐2,3‐di([²H₃]methyl)‐1,1‐dimethyl‐1H‐indene ( 6 ) (Scheme 1) [1]. However, it was not clear whether the transposition takes place through the successive migration of a Ph, a Me and again the Ph group (Scheme 2, Path A: shift IV → VII → VIIa ) or through Ph‐, Me‐, and then i‐Pr‐group (Scheme 2, Path B: IV → VII → VIIb ). The cyclialkylation of 3‐([²H₃]methyl)‐4‐methyl‐3‐phenylpentan‐2‐ol ( 7 ) yielded only one product, the 2,3‐dihydro‐2‐([²H₃]methyl)‐1,1,3‐trimethyl‐1H‐indene ( 8 ), in accordance with the migrations according to Path A. This result is also a support for the total mechanism proposed for the cyclialkylation of 4 (Scheme 2). The transition of a tertiary to a secondary carbenium ion is not definitely ensured (see [1]).     

Über Umlagerungen bei der Cyclialkylierung von Arylpentanolen zu 2,3‐Dihydro‐1H‐inden‐Derivaten, 5. Mitteilung

On Rearrangements by Cyclialkylations of Arylpentanols to 2,3‐Dihydro‐1 H ‐indene Derivatives. Part 5. The Acid‐Catalyzed Cyclialkylation of 2‐(2‐Chlorophenyl)‐2,4‐dimethylpentan‐3‐ol The mechanism proposed in [1] to explain the surprising result of the cyclialkylation of 4‐(2‐chlorophenyl)‐2,4‐dimethylpentan‐2‐ol ( 3 , R=Me), which gives not only the ‘normal' product, i.e., the 4‐chloro‐2,3‐dihydro‐1,1,3,3‐tetramethyl‐ ( 4 ), but also the isomer trans‐4‐chloro‐2,3‐dihydro‐1,1,2,3‐tetramethyl‐1H‐inden ( 5 ), could be differentiated in two sections (cf. Scheme 2): the first from 3 to the intermediary ion IIa ⇌ IIb , and the second from the latter ions to the final product 5 . For the first section, a sufficiently satisfactory explanation has been given in [1]; the second section has received important support from the mechanisms of the cyclialkylation of 2,4‐dimethyl‐2‐phenylpentan‐3‐ol ( 6 ), the precursor of II′a , the ion IIa without the o‐Cl substituent (cf. Schemes 2, 3 and 5 and [4]). The present communication gives an explanation of the influence of the o‐Cl substituent: a mechanism is proposed for the very complex cyclialkylation of 2‐(2‐chlorophenyl)‐2,4‐dimethylpentan‐3‐ol ( 11 ; cf. Scheme 9). Both mechanism may be considered as definitive. It is very surprising that, by the cyclialkylation of the compounds 1, 3, 8, 11, 15 , and 17 , only compound 1 gives the ‘normal' product; the cyclialkylation of all other phenylpentanols follows complex pathways including Et, i‐Pr, and Ph migrations, which could not be expected. In addition, it has been established that the transformation of 21 to 22 (cf. Scheme 12) and that of 23 to 24 (cf. Scheme 13) occur through two consecutive 1,2‐ and not through a single 1,3‐hydride migration or through an elimination‐addition process (cf. Scheme 13). It can be assumed that the transformation of ion IV (the 2‐(2‐chlorophenyl)‐3,4‐dimethylpent‐2‐ylium ion) to the ion V (the 4‐(2‐chlorophenyl)‐3,4‐dimethylpent‐2‐ylium ion (both shown in Scheme 9 as D‐isomers) occurs through the same pathway.     

A Novel,One‐Pot Four‐Component Route to 2′‐Thioxo‐2′,3′‐dihydrospiro[indole‐3,6′‐[1,3]thiazin]‐2‐one Derivatives

An efficient route to 2′,3′‐dihydro‐2′‐thioxospiro[indole‐3,6′‐[1,3]thiazin]‐2(1H)‐one derivatives is described. It involves the reaction of isatine, 1‐phenyl‐2‐(1,1,1‐triphenyl‐λ⁵‐phosphanylidene)ethan‐1‐one, and different amines in the presence of CS₂ in dry MeOH at reflux (Scheme 1). The alkyl carbamodithioate, which results from the addition of the amine to CS₂, is added to the α,β‐unsaturated ketone, resulting from the reaction between 1‐phenyl‐2‐(1,1,1‐triphenyl‐λ⁵‐phosphanylidene)ethan‐1‐one and isatine, to produce the 3′‐alkyl‐2′,3′‐dihydro‐4′‐phenyl‐2′‐thioxospiro[indole‐3,6′‐[1,3]thiazin]‐2(1H)‐one derivatives in excellent yields (Scheme 2). Their structures were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses.     

Reactions of Stable α‐Chlorosulfanyl Chlorides with CS‐Functionalized Compounds

The smooth reaction of 3‐chloro‐3‐(chlorosulfanyl)‐2,2,4,4‐tetramethylcyclobutanone ( 3 ) with 3,4,5‐trisubstituted 2,3‐dihydro‐1H‐imidazole‐2‐thiones 8 and 2‐thiouracil ( 10 ) in CH₂Cl₂/Et₃N at room temperature yielded the corresponding disulfanes 9 and 11 (Scheme 2), respectively, via a nucleophilic substitution of Cl^? of the sulfanyl chloride by the S‐atom of the heterocyclic thione. The analogous reaction of 3‐cyclohexyl‐2,3‐dihydro‐4,5‐diphenyl‐1H‐imidazole‐2‐thione ( 8b ) and 10 with the chlorodisulfanyl derivative 16 led to the corresponding trisulfanes 17 and 18 (Scheme 4), respectively. On the other hand, the reaction of 3 and 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazole‐5(4H)‐thione ( 12 ) in CH₂Cl₂ gave only 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazol‐5(4H)‐one ( 13 ) and the trithioorthoester derivative 14 , a bis‐disulfane, in low yield (Scheme 3). At ?78°, only bis(1‐chloro‐2,2,4,4‐tetramethyl‐3‐oxocyclobutyl)polysulfanes 15 were formed. Even at ?78°, a 1 : 2 mixture of 12 and 16 in CH₂Cl₂ reacted to give 13 and the symmetrical pentasulfane 19 in good yield (Scheme 5). The structures of 11, 14, 17 , and 18 have been established by X‐ray crystallography.     

Unexpected Thermal Transformation of Aryl 3‐Arylprop‐2‐ynoates: Formation of 3‐(Diarylmethylidene)‐2,3‐dihydrofuran‐2‐ones

A number of aryl 3‐arylprop‐2‐ynoates 3 has been prepared (cf. Table 1 and Schemes 3 – 5). In contrast to aryl prop‐2‐ynoates and but‐2‐ynoates, 3‐arylprop‐2‐ynoates 3 (with the exception of 3b ) do not undergo, by flash vacuum pyrolysis (FVP), rearrangement to corresponding cyclohepta[b]furan‐2(2H)‐ones 2 (cf. Schemes 1 and 2). On melting, however, or in solution at temperatures >150°, the compounds 3 are converted stereospecifically to the dimers 3‐[(Z)‐diarylmethylidene]‐2,3‐dihydrofuran‐2‐ones (Z)‐ 11 and the cyclic anhydrides 12 of 1,4‐diarylnaphthalene‐2,3‐dicarboxylic acids, which also represent dimers of 3 , formed by loss of one molecule of the corresponding phenol from the aryloxy part (cf. Scheme 6). Small amounts of diaryl naphthalene‐2,3‐dicarboxylates 13 accompanied the product types (Z)‐ 11 and 12 , when the thermal transformation of 3 was performed in the molten state or at high concentration of 3 in solution (cf. Tables 2 and 4). The structure of the dihydrofuranone (Z)‐ 11c was established by an X‐ray crystal‐structure analysis (Fig. 1). The structures of the dihydrofuranones 11 and the cyclic anhydrides 12 indicate that the 3‐arylprop‐2‐ynoates 3 , on heating, must undergo an aryl O→C(3) migration leading to a reactive intermediate, which attacks a second molecule of 3 , finally under formation of (Z)‐ 11 or 12 . Formation of the diaryl dicarboxylates 13 , on the other hand, are the result of the well‐known thermal Diels‐Alder‐type dimerization of 3 without rearrangement (cf. Scheme 7). At low concentration of 3 in decalin, the decrease of 3 follows up to ca. 20% conversion first‐order kinetics (cf. Table 5), which is in agreement with a monomolecular rearrangement of 3 . Moreover, heating the highly reactive 2,4,6‐trimethylphenyl 3‐(4‐nitrophenyl)prop‐2‐ynonate ( 3f ) in the presence of a twofold molar amount of the much less reactive phenyl 3‐(4‐nitrophenyl)prop‐2‐ynonate ( 3g ) led, beside (Z)‐ 11f , to the cross products (Z)‐ 11fg , and, due to subsequent thermal isomerization, (E)‐ 11fg (cf. Scheme 10), the structures of which indicated that they were composed, as expected, of rearranged 3f and structurally unaltered 3g . Finally, thermal transposition of [¹⁷O]‐ 3i with the ¹⁷O‐label at the aryloxy group gave (Z)‐ and (E)‐[¹⁷O₂]‐ 11i with the ¹⁷O‐label of rearranged [¹⁷O]‐ 3i specifically at the oxo group of the two isomeric dihydrofuranones (cf. Scheme 8), indicating a highly ordered cyclic transition state of the aryl O→C(3) migration (cf. Scheme 9).     

Photoaddition of thiocarboxylic acids to 2,3‐diallyltetraazathiapentalenes

Photoirradiation of acetone solutions of 2,3‐diallyl‐6,7‐dihydro‐5H‐2a‐thia(2a‐S^IV)‐2,3,4a, 7a‐tetraazacyclopent[cd]indene‐ 1,4(2H,3H)‐dithione ( 1 ) in the presence of excess thioacetic acid and thiobenzoic acid afforded addition products, 2,3‐bis(3‐acetylthiopropyl)‐ and 2,3‐bis(3‐benzoylthiopropyl)‐6,7‐dihydro‐5H‐2a‐thia(2a‐S^IV)2,3,4a, 7a‐tetraazacyclopent[cd]indene‐1,4(2H,3H)‐dithiones, respectively, in good yields. These photoaddition reactions were facilitated by the addition of oxygen.     

Heterocyclization reaction of 2‐(2‐methylaziridin‐1‐yl)‐3‐ureidopyridines under appel's conditions

The reaction of 2‐(2‐methylaziridin‐1‐yl)‐3‐ureidopyridines 12 with triphenylphosphine, carbon tetra‐chloride, and triethylamine (Appel's conditions) led to the corresponding carbodiimides 13 , which underwent intramolecular cycloaddition reaction with aziridine under the reaction conditions to give the pyridine‐fused heterocycles, 2,3‐dihydro‐1H‐imidazo[2′,3′:2,3]imidazo[4,5‐b]pyridines 16 and 12,13‐dihydro‐5H‐1,3 ‐benzodiazepino [2′,3′:2,3] imidazo[4,5‐b]pyridines 17 .     

Synthese und Reaktivität von 2‐Brom‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol Molekülstruktur von Bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐yl)

Synthesis and Reactivity of 2‐Bromo‐1,3‐diethyl‐2,3‐dihydro‐1 H ‐1,3,2‐benzodiazaborole Molecular Structure of Bis(1,3‐diethyl‐2,3‐dihydro‐1 H ‐1,3,2‐benzodiazaborol‐2‐yl The reaction of a slurry of calcium hydride in toluene with N,N′‐diethyl‐o‐phenylenediamine ( 1 ) and boron tribromide affords 2‐bromo‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol ( 2 ) as a colorless oil. Compound 2 is converted into 2‐cyano‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborole ( 3 ) by treatment with silver cyanide in acetonitrile. Reaction of 2 with an equimolar amount of methyllithium affords 1,3‐diethyl‐2‐methyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborole ( 4 ). 1,3,2‐Benzodiazaborole is smoothly reduced by a potassium‐sodium alloy to yield bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐yl] ( 7 ), which crystallizes from n‐pentane as colorless needles. Compound 7 is also obtained from the reaction of 2 and LiSnMe₃ instead of the expected 2‐trimethylstannyl‐1,3,2‐benzodiazaborole. N,N′‐Bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐ yl)‐1,2‐diamino‐ethane ( 6 ) results from the reaction of 2 with Li(en)C≡CH as the only boron containing product. Compounds 2 – 4 , 6 and 7 are characterized by means of elemental analyses and spectroscopy (IR, ¹H‐, ¹¹B{¹H}‐, ¹³C{¹H}‐NMR, MS). The molecular structure of 7 was elucidated by X‐ray diffraction analysis.     

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.     

NMR analysis of a series of 1,2‐bis(1‐R‐5‐oxo‐2,3‐dihydro‐1H‐pyrrol‐4‐ylidene)ethanes and X‐ray crystal structure analysis of the R = mesityl compound

Four tetramethyl 4,4′‐(ethane‐1,2‐diylidene)bis[1‐R‐5‐oxo‐4,5‐dihydro‐1H‐pyrrole‐2,3‐dicarboxylate] compounds, denoted class (1), are a series of conjugated buta‐1,3‐dienes substituted with a heterocyclic group. The compounds can be used as dyes and pigments due to their long‐range conjugated systems. Four structures were studied using ¹H NMR, ¹³C NMR and mass spectroscopy, viz. with R = 2,4,6‐trimethylphenyl, (1a), R = cyclohexyl, (1b), R = tert‐butyl, (1c), and R = isopropyl, (1d). A detailed discussion is presented regarding the characteristics of the three‐dimensional structures based on NMR analysis and the X‐ray crystal structure of (1a), namely tetramethyl 4,4′‐(ethane‐1,2‐diylidene)bis[5‐oxo‐1‐(2,4,6‐trimethylphenyl)‐4,5‐dihydro‐1H‐pyrrole‐2,3‐dicarboxylate], C₃₆H₃₆N₂O₁₀. The conjugation plane and stability were also studied via quantum chemical calculations.     

A Facile One‐Pot Synthesis of Functionalized 1,5‐Dihydro‐2H‐[1]benzopyrano[2,3‐b]pyridin‐5‐ones

The highly reactive 1 : 1 intermediate generated in the reaction between dialkyl acetylenedicarboxylate (=but‐2‐ynedioic acid dialkyl ester) 4 and triphenylphosphine was trapped by 2‐amino‐4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehydes 5 to yield highly functionalized dialkyl‐1,5‐dihydro‐5‐oxo‐1‐phenyl‐2H‐[1]benzopyrano[2,3‐b]pyridine‐2,3‐dicarboxylates in high yield.     

Surprising Formation of Highly Substituted Azulenes on Thermolysis of 4,5,6,7,8‐Pentamethyl‐2H‐cyclohepta[b]furan‐2‐one and Heptalene Formation with the New Azulenes

Heating of 4,5,6,7,8‐pentamethyl‐2H‐cyclohepta[b]furan‐2‐one ( 1a ) in decalin at temperatures >170° leads to the development of a blue color, typical for azulenes. It belongs, indeed, to two formed azulenes, namely 4,5,6,7,8‐pentamethyl‐2‐(2,3,4,5,6‐pentamethylphenyl)azulene ( 4a ) and 4,5,6,7,8‐pentamethylazulene ( 5a ) (cf. Scheme 2 and Table 1). As a third product, 4,5,6,7‐tetramethyl‐2‐(2,3,4,5,6‐pentamethylphenyl)‐1H‐indene ( 6a ) is also found in the reaction mixture. Neither 4,6,8‐trimethyl‐2H‐cyclohepta[b]furan‐2‐one ( 1b ) nor 2H‐cyclohepta[b]furan‐2‐one ( 1c ) exhibit, on heating, such reactivity. However, heating of mixtures 1a / 1b or 1a / 1c results in the formation of crossed azulenes, namely 4,6,8‐trimethyl‐2‐(2,3,4,5,6‐pentamethylphenyl)azulene ( 4ba ) and 2‐(2,3,4,5,6‐pentamethylphenyl)azulene ( 4ca ), respectively (cf. Scheme 3). The formation of small amounts of 4,6,8‐trimethylazulene ( 5ba ) and azulene ( 5ca ), respectively, besides 1H‐indene 6a is also observed. The observed product types speak for an [8+2]‐cycloaddition reaction between two molecules of 1a or between 1b and 1c , respectively, with 1a , whereby 1a plays in the latter two cases the part of the two‐atom component (cf. Figs. 5 – 7 and Schemes 4 – 6). Strain release, due to the five adjacent Me groups in 1a , in the [8+2]‐cycloaddition step seems to be the driving force for these transformations (cf. Table 3), which are further promoted by the consecutive loss of two molecules of CO₂ and concomitant formation of the 10π‐electron system of the azulenes. The new azulenes react with dimethyl acetylenedicarboxylate (ADM) to form the corresponding dimethyl heptalene‐4,5‐dicarboxylates 20 , 22 , and 24 (cf. Scheme 7), which give thermally or photochemically the corresponding double‐bond‐shifted (DBS) isomers 20′ , 22′ , and 24′ , respectively. The five adjacent Me groups in 20 / 20′ and 24 / 24′ exert a certain buttressing effect, whereby their thermal DBS process is distinctly retarded in comparison to 22 / 22′ , which carry `isolated' Me groups at C(6), C(8), and C(10). This view is supported by X‐ray crystal‐structure analyses of 22 and 24 (cf. Fig. 8 and Table 5).     

Synthesis and Halogen Bonding in the Crystal Structures of the New 2,3‐Diiodo Indenone and 1‐Ethoxy‐2,3‐diiodo Indene

The CuI‐catalyzed addition of iodine to the C≡C triple bond of 3,3‐diethoxy‐1‐phenyl propyne ( 1 ) unexpectedly leads to the new cyclization products 2,3‐diiodo‐1H‐inden‐1‐one ( 2 ) and 1‐ethoxy‐2,3‐diiodo‐1H‐indene ( 3 ). Both compounds were isolated and characterized via ¹H, ¹³C NMR (Nuclear Magnetic Resonance) spectroscopy and HRMS (High Resolution Mass Spectrometry). The molecular and crystal structures of compounds 2 and 3 were determined by single crystal X‐ray diffraction. Their crystal structures are governed by extensive halogen bonding, involving I·I and I·O interactions.     

Rhodium(III)‐Catalyzed [3+2] Annulation of 5‐Aryl‐2,3‐dihydro‐1H‐pyrroles with Internal Alkynes through C(sp2)H/Alkene Functionalization

This study describes a new rhodium(III)‐catalyzed [3+2] annulation of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles with internal alkynes using a Cu(OAc)₂ oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp²)? H bond and addition/protonolysis of an alkene C?C bond. This method is applicable to a wide range of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles and internal alkynes, and results in the assembly of the spiro[indene‐1,2′‐pyrrolidine] architectures in good yields with excellent regioselectivities.     

Eight 7‐benzyl‐3‐tert‐butyl‐1‐phenylpyrazolo[3,4‐d]oxazines,encompassing structures containing no intermolecular hydrogen bonds,and hydrogen‐bonded structures in one,two or three dimensions

7‐Benzyl‐3‐tert‐butyl‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₂H₂₅N₃O, (I), and 3‐tert‐butyl‐7‐(4‐methylbenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₃H₂₇N₃O, (II), are isomorphous in the space group P2₁, and molecules are linked into chains by C—H...O hydrogen bonds. In each of 3‐tert‐butyl‐7‐(4‐methoxybenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₃H₂₇N₃O₂, (III), which has cell dimensions rather similar to those of (I) and (II), also in P2₁, and 3‐tert‐butyl‐1‐phenyl‐7‐[4‐(trifluoromethyl)benzyl]‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₃H₂₄F₃N₃O, (IV), there are no direction‐specific interactions between the molecules. In 3‐tert‐butyl‐7‐(4‐nitrobenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₂H₂₄N₄O₃, (V), a combination of C—H...O and C—H...N hydrogen bonds links the molecules into complex sheets. There are no direction‐specific interactions between the molecules of 3‐tert‐butyl‐7‐(2,3‐dimethoxybenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₄H₂₉N₃O₃, (VI), but a three‐dimensional framework is formed in 3‐tert‐butyl‐7‐(3,4‐methylenedioxybenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₃H₂₅N₃O₃, (VII), by a combination of C—H...O, C—H...N and C—H...π(arene) hydrogen bonds, while a combination of C—H...O and C—H...π(arene) hydrogen bonds links the molecules of 3‐tert‐butyl‐1‐phenyl‐7‐(3,4,5‐trimethoxybenzyl)‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₅H₃₁N₃O₄, (VIII), into complex sheets. In each compound, the oxazine ring adopts a half‐chair conformation, while the orientations of the pendent phenyl and tert‐butyl substituents relative to the pyrazolo[3,4‐d]oxazine unit are all very similar.     

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).     

Iodine‐Catalyzed Synthesis of Spiro[1,3,4‐benzotriazepine‐2,3′‐indole]‐2′,5(1H,1′H)‐diones under Mild Conditions

The I₂‐catalyzed preparation of spiro[1,3,4‐benzotriazepine‐2,3′‐indole]‐2′,5(1H,1′H)‐diones from 2‐aminobenzohydrazide and isatins in MeCN at room temperature in good‐to‐excellent yields is described. The structure of 3 was corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS data). A plausible mechanism for this type of reaction is proposed (Scheme 2).     

Synthesis of 2‐Aryl‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐2,5‐dihydro‐1H‐pyrrole‐3‐carboxylates by the Reaction between Hydrazones,Acetylenedicarboxylates, and 1‐Aryl‐N,N′‐bis(arylmethylidene)methanediamines

An efficient approach for the preparation of functionalized 2‐aryl‐2,5‐dihydro‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐1H‐pyrroles is described. The four‐component reaction between aldehydes, NH₂NH₂?H₂O, dialkyl acetylenedicarboxylates, and 1‐aryl‐N,N′‐bis(arylmethylidene)methanediamines proceeds in EtOH under reflux in good‐to‐excellent yields (Scheme 1). The structures of 4 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS, and, in the case of 4f , by X‐ray crystallography). A plausible mechanism for this type of reaction is proposed (Scheme 2).