Fragmentierung von α-Aminoketoximen. IV. Teil Der Einfluss sterischer. Faktoren Fragmentierungsreaktion, 17. Mitteilung

(N-Methyl-2-piperidyl)phenyl ketoxime acetate( 10b ) and (N-methyl-2-pyrrolidinyl)-phenyl ketoxime acetate ( 13b ) undergo quantitative fragmentation in 80% ethanol to yield benzonitrile and the cyclic imonium salts 11 and 14 . Their reaction rates are approx. 10⁷ and 10⁸, respectively, as high as those calculated for the homomorphous compounds, viz. 2-methylcyclohexylphenyl ketoxime acetate ( 12b ) and 2-methylcyclopentylphenyl ketoxime acetate ( 15b ), which undergo quantitative Beckmann rearrangement. Synchronous fragmentation therefore provides a very large driving force for ionisation, even when the stereo-electronically suitable conformation is not the prevalent one, as with 10b .     

Photoinduzierte Cycloadditionen von 2,2-Dimethyl-3-phenyl-2H-azirin an Nitrile und «push-pull»-Olefine. 43. Mitteilung über Photoreaktionen

Photoinduced Cycloadditions of 2,2-Dimethyl-3-phenyl-2H-azirine with Nitriles and ‘push-pull’ Olefines. Electron deficient nitriles of the type 5a–e in contrast to nonactivated nitriles undergo regiospecific [2+3]cycloadditions to benzonitrile isopropylide ( 2b ), which was generated in situ by irradiation of 2,2-dimethyl-3-phenyl-2H-azirine ( 1b ), to yield the 2H-imidazole derivatives 6a – e (Scheme 2). The structure of the photoproducts was mainly deduced from ¹³C-NMR. and mass spectrometry. Whereas normal olefins or enolethers do not react with 2b , push-pull olefins of the type 10a – d readily undergo the cycloaddition to give the 3-alkoxy-5,5-dimethyl-2-phenyl-1-pyrrolines 11a – d (Scheme 3 and 4). The structure of the photoproducts 11a – d indicates that the regiospecificity of the cycloaddition corresponds to that of acrylonitriles and acrylesters with 2b .     

Reaktionen von 3-Dimethylamino-2,2-dimethyl-2H-azirin mit Phenolen und Halogenaromaten

Reactions of 3-dimethylamino-2,2-dimethyl-2H-azirine with phenols and aryl halides The reactions of 3-dimethylamino-2,2-dimethyl-2H-azirine ( 1 ) with phenols are described in chap. 1. The azirine 1 reacts with the 2-formyl- and 2-acetylphenols 5 – 8 to yield the N′-methylidene derivatives of 2-amino-N,N-dimethyl-isobutyramide 9 - 12 (Scheme 2, tautomeric form b ). These products are in equilibrium with the tautomeric quinoide forms 9a-12a . Under similar conditions 4-hydroxybenzaldehyde did not react with 1 . Reaction of 1 with 4-hydroxycoumarine ( 13 ) gives the 4-amino-coumarine 14 (Scheme 2). The mechanism of these reactions is analogous to the previously reported one for the reaction of 1 with cyclic enolisable 1,3-diketones [2] [3]. Activated phenols with pK_a-values < 8, e.g. 2- and 4-nitrophenol, 2,4-dinitrophenol and pentachlorophenol, undergo addition reactions with 1 in boiling benzene solution to give the aniline derivatives 15 - 18 (Scheme 3). A reaction mechanism is given in Scheme 3: after protonation of the azirine 1 followed by attack of the phenolate ion at the amidinium-C-atom, the intermediate of type e undergoes a rearrangement to the spiro-Meisenheimer complexes of type f . Ring opening leads to 15 – 18 . A similar reaction is observed for 2,4-dinitro-thiophenol and 1 , giving 2-(N′-(2,4-dinitrophenyl)amino)-N,N-dimethyl-isobutyrothioamide ( 19 ). The azirine 1 reacts with the more acidic 2,4,6-trinitrophenol (picric acid) to yield 3,3,6,6-tetramethylpiperazine-2,5-bis(N,N-dimethyliminium) dipicrate ( 21 , Scheme 4). The methacrylamidinium salt 22 is the only product (97% yield) in the reaction of 8-hydroxy-5,7-dinitroquinoline and 1 in acetonitrile solution. The reaction of 1 with picric acid can be explained in a similar way as the previously reported one with strong acids (cf. Scheme 1, [1] [3] [5]). An alternative mechanism without formation of the 1-aza-allylcation c is postulated in Scheme 5, together with a mechanism which could explain the exclusive formation of 22 in the reaction of 1 with 8-hydroxy-5,7-dinitroquinoline. In chap. 2 a few reactions of the azirine 1 with aryl halides are reported. In the reaction with 2,4-dinitrofluorobenzene it is shown by UV. and NMR., that m , n and o are intermediates (Scheme 6). Working up the reaction mixture with water, hydrogen sulfide or benzylamine leads to the aniline derivatives 17 , 19 and 26 , respectively. With picryl chloride and 8-hydroxy-5,7-dinitroquinoline the azirine 1 undergoes a nucleophilic aromatic substitution to afford the intermediates p and q , which via deprotonation and ring opening give acrylamidine derivatives ( 27 and 29 , Scheme 7 and 8). The steric hindrance in p and q between the aziridine ring and the two groups in o-position could be the reason for the different behaviour of the intermediates n and p or q (cf. Schemes 6 and 8).     

Synthese und Reaktionen 8-gliedriger Heterocyclen aus 3-Dimethylamino-2,2-dimethyl-2H-azirin und Saccharin bzw. Phthalimid

Synthesis and Reactions of 8-membered Heterocycles from 3-Dimethylamino-2,2-dimethyl-2H-azirine and Saccharin or Phthalimide 3-Dimethylamino-2,2-dimethyl-2H-azirine ( 1 ) reacts at 0-20° with the NH-acidic compounds saccharin ( 2 ) and phthalimide ( 8 ) to give the 8-membered heterocycles 3-dimethylamino-4,4-dimethyl-5,6-dihydro-4 H-1,2,5-benzothiadiazocin-6-one-1,1-dioxide ( 3a ) and 4-dimethylamino-3,3-dimethyl-1,2,3,6-tetrahydro-2,5-benzodiazocin-1,6-dione ( 9 ), respectively. The structure of 3a has been established by X-ray (chap. 2). A possible mechanism for the formation of 3a and 9 is given in Schemes 1 and 4. Reduction of 3a with sodium borohydride yields the 2-sulfamoylbenzamide derivative 4 (Scheme 2); in methanolic solution 3a undergoes a rearrangement to give the methyl 2-sulfamoyl-benzoate 5 . The mechanism for this reaction as suggested in Scheme 2 involves a ring contraction/ring opening sequence. Again a ring contraction is postulated to explain the formation of the 4H-imidazole derivative 7 during thermolysis of 3a at 180° (Scheme 3). The 2,5-benzodiazocine derivative 9 rearranges in alcoholic solvents to 2-(5′-dimethylamino-4′,4′-dimethyl-4′H-imidazol-2′-yl) benzoates ( 10 , 11 ), in water to the corresponding benzoic acid 12 , and in alcoholic solutions containing dimethylamine or pyrrolidine to the benzamides 13 and 14 , respectively (Scheme 5). The reaction with amines takes place only in very polar solvents like alcohols or formamide, but not in acetonitrile. Possible mechanisms of these rearrangements are given in Scheme 5. Sodium borohydride reduction of 9 in 2-propanol yields 2-(5′-dimethylamino-4′,4′-dimethyl-4′H-imidazol-2′-yl)benzyl alcohol ( 15 , Scheme 6) which is easily converted to the O-acetate 16 . Hydrolysis of 15 with 3N HCl at 50° leads to an imidazolinone derivative 17a or 17b , whereas hydrolysis with 1N NaOH yields a mixture of phthalide ( 18 ) and 2-hydroxymethyl-benzoic acid ( 19 , Scheme 6). The zwitterionic compound 20 (Scheme 7) results from the hydrolysis of the phthalimide-adduct 9 or the esters 11 and 12 . Interestingly, compound 9 is thermally converted to the amide 13 and N-(1′-carbamoyl-1′-methylethyl)phthalimide ( 21 , Scheme 7) whose structure has been established by an independent synthesis starting with phthalic anhydride and 2-amino-isobutyric acid. However, the reaction mechanism is not clear at this stage.     

Studies on furan derivatives IV. A simple preparation of α-substituted β-(5-nitro-2-furyl)ethynyls from α-substituted β-(5-nitro-2-furyl)vinylamines

α-Substituted β-(5-nitro-2-furyl)ethynyls were conveniently prepared by the deamination of α-substituted β-(5-nitro-2-furyl)vinylamines. Also the application of this reaction toward α,β-bis(p-nitrophenyl)vinylamine was examined and afforded α,β-bis(p-nitrophenyl)ethynyl as the main product.     

Zur Aktivierung partiell silylierter Kohlenhydrate mittels Triphenylphosphan/Azodicarbonsäureester

On the Activation of Partially Silylated Carbohydrates Using Triphenylphosphane/Diethylazodicarboxylate Reaction of methyl α-D-glucopyranoside ( 1 ) with two equivalents of t-butyldimethylchlorosilane yields methyl 2,6-bis[O-(t-butyldimethylsilyl)]-α-D-glucopyranoside ( 1a ) and methyl 3,6-bis[O(t-butyldimethylsilyl)]-α-D-glucopyranoside ( 1b ) in a ratio of 4:1. The anomeric β-pyranoside 2 affords methyl 2,6-bis[O(t-butyldimethylsilyl)]-β-D-glucopyranoside ( 2a ) and methyl 3,6-bis[O(t-butyldimethylsilyl)]-β-D-glucopyranoside ( 2b ) in nearly equal amounts. 2b is isomerized to methyl 4,6-bis[O(t-butyldimethylsilyl)]-β;-D-glucopyranoside ( 2c ) (83%) and 2a (10%) with triphenylphosphane/diethylazodicarboxylate. Structures were assigned by NMR.-analysis and CD.-analysis of the corresponding benzoates 1c , 1d and 2d and of the acetates 2e and 2f . 1a is transformed into methyl 4-azido-2, 6-bis[O(t-butyldimethylsilyl)]-4-deoxy-α-D-galactopyranoside ( 3 ) with triphenylphosphane/diethylazodicarboxylate/HN₃. 2a and 2c yield the 3-azido-allosides 5 and 7 respectively under similar conditions. The activation by triphenylphosphane/diethylazodicarboxylate is high enough to introduce also p-nitrobenzoate groups with inversion of configuration at the reaction center. By this way 1a and 2a give methyl 2, 6-bis[O(t-butyldimethylsilyl)]-4-O-p-nitrobenzoyl-α-D-galactopyranoside ( 4 ) and methyl 2, 6-bis[O-(t-butyldimethylsilyl)]-3-O?ptrobenzoyl-β-D-allopyranoside ( 6 ) respectively. For elucidation of structures the acetate derivatives 3a-7a were prepared.     

Additionen von 2,2-Dimethyl-3-dimethylamino-2H-azirin an 2-Formyl-cycloalkanone und Sulfinsäuren

2,2-Dimethyl-3-dimethylamino-2H-azirine ( 1 ) reacts with the formyl-cycloalkanones 4 – 8 in boiling benzene to give the 1:1 adducts 13 – 17 in 60–99% yield (Table). These adducts are N′-[(2-oxo-cycloalkylidene)-methyl] derivatives of 2-amino-N, N-dimethylisobutyramide. The reaction mechanism (Scheme 6) is analogous to the mechanism of the reaction of 1 with carboxylic acids and cyclic enolisable 1,3-diketones [1]. Sulfinic acids and 1 undergo a similar reaction at ?15° to yield 2-sulfinamido-N, N-dimethylisobutyramides (Schemes 4 and 7), while sulfonic acids and the azirine 1 lead to a dimeric salt of type 20 , which with sodium hydroxide gives the dihydropyrazine 21 (Scheme 5).     

Herstellung und Reaktionen der valenzpolaromeren Verbindung (4,4-Dimethyl-2-thiazolin-5-dimethyliminium)-2-thiolat ⇌ (1-Dimethylthiocarbamoyl-1-methyl-äthyl)-isothiocyanat aus 3-Dimethyl-amino-2,2-dimethyl-2H-azirin und Schwefelkohlenstoff

Synthesis and reactions of the valence polaromeric compound (4,4-dimethyl-2-thiazoline-5-dimethyliminium)-2-thiolate ? 1-dimethylthiocarbamoyl-1-methyl-ethyl isothiocyanate from 3-dimethylamino-2,2-dimethyl-2H-azirine and carbon disulfide. 3-Dimethylamino-2,2-dimethyl-2H-azirine ( 1 ) reacts with carbon disulfide to give crystals which have the dipolar structure 3a [(4,4-dimethyl-2-thiazoline-5-dimethyliminium)-2-thiolate, Scheme 1]. In solution, the non-dipolar (charge-free) isomeric form 3b (1-Dimethyl-thiocarbamoyl-1-methyl-ethyl isothiocyanate) is almost exclusively populated. Reaction products are derived from both forms: Derivatives of 3a are the hydrolysis product 6 , the sodium borohydride reduction product 7 and the methylation products 9 and 10 , respectively (Scheme 2). The isothiocyanate form 3b is responsible for the various reaction products with amines (Scheme 3). One of the reaction products with ammonia, namely 20 , is also obtained by the reaction of 1 with thiocyanic acid. Thermolysis of the azirine/carbon disulfide adduct 3 leads to 2-dimethylamino-4,4-dimethyl-2-thiazoline-5-thione ( 17 ) in high yield. A possible mechanism is outlined in Scheme 4. The same compound is also formed by rearrangement of 3 under the catalytic influence of dimethylamine. Its structure has been established by X-ray crystallography (section 4). Again a rearrangement is involved in the reductive (NaBH₄) conversion of 17 to 7 , the direct reduction product of the dipolar species 3a (Scheme 5). The isothiocyanate form 3b is able to react with a second molecule of 3-dimethylamino-2,2-dimethyl-2H-azirine ( 1 ) to yield compound 25 , which in the crystalline or dissolved state appears to be almost entirely populated by the carbodiimide form with structure 25b (Scheme 7), though all reaction products of 25 (reduction with sodium borohydride, addition of water or hydrogen sulfide, Schemes 7 and 8) are derived from the dipolar form 25a , not detectable as such; here again therefore there is a dynamic equilibrium 25a ? 25b . The two forms of adduct 3 , namely 3a and 3b , are obviously very easily interconverted at room temperature and therefore can be considered as valence polaromeric forms (section 5). A classification of the dipolar (zwitterionic) form is given, which allows a comparison of various dipolar species and gives as indication of charge stabilization by delocalization. The versatile reactivity of the 3-dimethylamino-2,2-dimethyl-2H-azirine/carbon disulfide adduct is demonstrated by the fact that with simple reagents approximately 25 derivatives have been obtained, most of them being new heterocyclic compounds.     

Die Struktur des Adduktes aus 3-Dimethylamino-2,2-dimethyl-2H-azirin und 3-Methyl-2,4-diphenyl-1,3-oxazolium-5-olat. Vorläufige Mitteilung

Structure of the adduct from 3-dimethylamino-2,2-dimethyl-2H-azirine and 3-methyl-2,4-diphenyl-1,3-oxazolium-5-olate 3-Dimethylamino-2,2-dimethyl-2H-azirine ( 1 ) reacts with 3-methyl-2,4-diphenyl-1,3-oxazolium-5-olate ( 5a ) to give a 1:1 adduct ( 7 ) in a 88% yield. Its crystal structure has been determined by X-ray analysis (direct methods) and refined with 1056 structure amplitudes to R = 0,032. The crystal system is monoclinic, space group P2₁/c, with unit cell dimensions a = 10.663, b = 9,828, c = 18,592 Å, and β = 90,63°. It is obvious that 4-dimethylamino-5,5-dimethyl-2-[α-(N-methyl-benzamido)benzyliden]-Δ³-1,3-oxazoline ( 7 ) arises from an addition of 1 to the valence-polaromeric ketene form 5b of the mesoionic oxazolone 5a (Scheme 3).     

Reactions of donor-substituted furans with electrophilic ethylenes

2-Methoxyfuran and 2-p-tolyloxyfuran were attacked at the 5-position by tetracyanoethylene or the super-electrophilic 2,2-bis(trifluoromethyl)ethylene-1,1-dicarbonitrile affording (Z)-3-cyclopropylacrylic esters, substituted in the 3-membered ring. Initially formed zwitterions undergo simultaneous opening of the furan and closure of the cyclopropane ring. In the presence of pyridine, 1,3-prototropy converts the zwitterion to 5-substitution products of the furans.     

Beckmann-Umlagerung und Fragmentierung,IV. Teil. 5- und 7-Zentren-Fragmentierung von γ-Keto-ketoximen: Fragmentierungsreaktionen, 21. Mitteilung

A heterolytic 7-centre fragmentation reaction of the type a-b-c-d-e-f-X → a b + c = d + e = f + X has been demonstrated for the first time utilizing γ-keto-ketoximes. This system may also undergo a novel 5-centre fragmentation. With sodium hydroxide in aqueous ethanol and with sodium ethoxide in ethanol the p-toluene-sulfonate of 1-oxo-9-methyl-5-oximino-trans-decalin (7b) is converted quantitatively into 9-cyano-6-methyl-non-5-enoic acid (10b) and the corresponding ethyl ester, respectively. With lower concentrations of nucleophile normal Beckmann rearrangement to the lactam 13a and the lactimether 19b predominates. In the case of the p-toluenesulfonate of the 9-nor-derivative 7a a base-induced 5-centre fragmentation reaction to the α,β-unsaturated ketone 12 competes with 7-centre fragmentation to 9-cyano-non-5-enoic acid (10a), strong bases favouring the former reaction. In the absence of strong bases of nucleophiles Beckmann rearrangement again dominates.     

Die Struktur einer stabilen dipolaren Verbindung aus 2,2-Dimethyl-3-dimethylamino-2H-azirin und Benzoylisothiocyanat. Vorläufige Mitteilung

Structure of a Stable Dipolar Compound from 2,2-Dimethyl-3-dimethylamino-2H-azirine and Benzoylisothiocyanate. Benzoylisothiocyanate and 2,2-dimethyl-3-dimethylamino-2H-azirine ( 1 ) react to given the dipolar compound 4,4-dimethyl-2-thiazolin-5-dimethylimminium-2-benzcarboxamidate ( 2 ), whose structure has been proved by X-ray analysis. Compound 2 , upon addition of water, yields the thiourea derivative 3 , whereas by acid catalyzed hydrolysis the thiazolinone derivative 4 is formed. The dipolar structure 2 is also existent in organic solvents like dimethylsulfoxide or chloroform.     

(Perhalogenmethylthio)heterocyclen. XXI. Reaktionen halogenierter perhalogenmethylthiopyrrole: Salz- und radikalbildung,dimerisierung

2-Chloro-3,4,5-tris(trifluoromethylthio)pyrrole ( 2a ), 3-Chloro-2,4,5-tris(trifluoromethylthio)pyarrole ( 2b ) and 3,4-dichloro-2,5-bis(trifluromoethylthio)pyrrole ( 2c ) react with silver nitrate/silver acetate in good yield to give the corresponding N-silver salts 3a-c . Compound 2b forms with an aqueous potassium hydroxide solution the N-potassium salt 4 . Compounds 3a and 3b react with iodine to give the dimeers 2,2′-dichloro-3,3,′ 4,4′5,5′-hexakis(trifluoromethylthio)-2,2′-bi-2H-pyrrolyl ( 5a ) and 3,3′-dichloro-2,2′,4,4′,5,5′-hexakis(trifluoromethylthio)-2,2′-bi-2H-pyrrolyl ( 5b ). The dimers dissociate in solution to the corresponding pyrrolayl radicals. The esr and endor spectra of 3-chloro-2,4,5-tris(trifluoromethylthio)pyrrolyl were measured; coupling constants are given. For the newly prepared substances melting-points, ¹⁹F-nmr and ir spectroscopical data are provided.     

Synthesis and liquid crystalline properties of novel pyridine derivatives

The treatment of 4‐hydroxypyridine with cholestery p‐(ω‐bromoalkyloxy)benzoates in N,N‐dimethylformamide containing K₂CO₃ gave cholestery p‐[ω‐(4‐pyridyloxy)alkyloxy]benzoates, which exhibited liquid crystalline properties     

Beckmann Fragmentation and Rearrangement. Part VI thian-3-one oximes. Fragmentation reactions no. 26

In 70% aqueous dioxane thian-3-one anti-oxime p-toluenesulfonate (tosylate) ( 8b ) undergoes concerted fragmentation to the methylidenesulfonium ion 14 , part of which recyclizes to 1,3-thiazepin-4-one ( 11 ). With the syn-isomer 8b rearrangement to 1,4-thiazepin-3-one ( 10 ) and fragmentation to 14 occur in the ratio 4:1. Analysis of the rate data in 80% ethanol shows that anti fragmentation is 142 times as fast as syn fragmentation, but only 26 times as fast as rearrangement of the ‘homomorphous’ thian-4-one oxime tosylate ( 18b ). A comparison of the rates of cyclohexanone oxime tosylate 20 , thian-3- and -4-one oxime tosylates reveals the rate retarding influence of sulfur. – The configurations assigned to the stereoisomeric thian-3-one oximes ( 8a ) in the literature have to be reversed in the light of present results.     

Synthesis and characterization of certain new poly(bisimide)s. I

Maleic and citraconic anhydrides were reacted with several diamines to obtain a novel class of high temperature resistant bisimides.^1–3 The bisimides were characterized by melting points, elemental analysis, UV–Vis, ¹H- and ¹³C-NMR, and mass spectral analysis. The bisimide monomers were then polymerized by the addition process. A poly(amidemaleimide) was also synthesized by reacting maleic anhydride with p-aminobenzhydrazide. The thermal stability of these highly crosslinked poly(bisimide)s were examined by TGA and DTA. A neat bisimide monomer obtained from 2,2′-bis[4(p-aminophenoxy)phenyl] propane with maleic anhydride namely, 2,2′-bis[4-(p-maleimidophenoxy)phenyl]propane was reacted with 2,2′-bis[4(p-aminophenoxy)phenyl]propane by the Michael reaction.⁴ A fiber glass cloth reinforced laminate was prepared from bismaleimide and amine mixture and the mechanical properties of the test laminate evaluated.     

Die heterolytische Fragmentierung von Benzoin-O-(carbamoyl)oximen

The Heterolytic Fragmentation of Benzoin-O-(carbamoyl)oximes While the known heterolytic fragmentation reactions give only three, thermal decomposition of benzoin-O-(carbamoyl)oximes results in at least four fragments: nitrile or isocyanide, carbonyl compound, CO₂ and amine. This exception is due to the transformation of the nucleofugal group 3 into the unstable carbamic acid and its decomposition (s. Scheme 1). Since only the configuration of benzoin (E)-O-(carbamoyl)oximes is satisfactory for concerted reactions, we conclude that the nitrile producing fragmentation of these (E)-compounds is concerted, whereas in the isocyanide producing fragmentation of the corresponding (Z)-compounds several steps are involved. – In contrast to the benzoin-O-(carbamoyl)oximes the pyrolysis of benzil-(E)-O-(methylcarbamoyl)oxime starts with the elimination of methyl isocyanate and the following fragmentation is that of the oxime.     

Beckmann-Umlagerung und Fragmentierung,III. Teil Versuche zur 7-Zentren-Fragmentierung eines γ-Aminoketoxims: Fragmentierungsreaktionen, 20. Mitteilung

In aqueous dioxane the p-toluenesulfonate 11B of 1β-dimethylamino-5-oximino-trans-decalin (11a) undergoes almost quantitative Beckmann rearrangement to the lactam 23. Approx. 1%, only, of the product of so-called 7-centre fragmentation, i.e. trans-9-cyano-non-5-enal (14) is detectable. Furthermore, the picryl ether 11C of the oxime 11a reacts at a normal rate. The results confirm the conclusion reached earlier, namely that fragmentation cannot compete with the Beckmann rearrangement in the case of γ-amino ketoximes, in contrast to the behaviour of α-amino ketoximes.     

Thermische Reaktionen mit 3-Phenyl-2H-azirinen; 1, 3-dipolare Cycloadditionen und En-Reaktionen

Benzonitrile p-nitrobenzylide ( 5 ) undergoes 1,3-dipolar cyclo-additions in the presence of 3-phenyl-2H-azirines ( 1 ), yielding in benzene at 0° 2-(p-nitrophenyl)-4,5-diphenyl-1,3-diazabicyclo[3.1.0]hex-3-enes ( 7 , scheme 2). Under the basic conditions of the reaction mixture, 7 a and 7 b are partially converted to 2-(p-nitrophenyl)-4,5-diphenyl-1,6-dihydropyrimidines ( 8a, b ) which are dehydrogenated by oxygen to the corresponding pyrimidines 9a and 9b , respectively. 3-Phenyl-2H-azirines ( 1 ) form, on heating at 145° in xylene in the presence of the azalactone 32 (2,4-diphenyl-Δ²-oxazolin-5-one), 4-(aziridin-2′-yl)-2,4-diphenyl-Δ²-oxazolin-5-ones ( 33 , scheme 11). 33 arises from an ene reaction of the enol form of 32 with 1 . Similar ene reactions are observed with the azirines 1 and dimedone ( 37 , scheme 12). Under the ene reaction conditions (xylene, 145°), the non-isolated intermediate primary adducts ( 38a and 38b ) undergo rearrangements of the vinylcyclopane-cyclopentene type to give 6,6-dimethyl-4-oxo-1,3-diphenyl-4, 5, 6, 7-tetrahydroisoindole ( 40 ) and 6, 6-dimethyl-4-oxo-3-phenyl-4, 5, 6, 7-tetrahedroindole ( 42 ), respectively.     

Synthesis and reactivities of 10-S-3 trithiadiazapentalene derivatives

1,3-Bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidinethiones 3a-f reacted with bromine to give trithiadiazapentalene derivatives 5a-f , bearing the exocyclic C-N double bonds, in moderate yields. The molecular structure of 5b was elucidated by the X-ray crystallographic analysis. The treatment of 5b-f with hydrochloric acid gave the ring-opening products, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazo-lidinones 9b-f , accompanied by the production of elemental sulfur. Reduction of 5b , 5d , and 5e with sodium borohydride gave the ring-opening compounds, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidines 13b , 13d , and 13e respectively.