Additionsreaktion von 3-Dimethylamino-2,2-dimethyl-2H-azirin mit Phenylisothiocyanat

Reaction of 3-Dimethylamino-2,2-dimethyl-2H-azirine with Phenyl Isothiocyanate In contrast to the reactions of 3-dimethylamino-2,2-dimethyl-2H-azirine ( 1a ) with various isothiocyanates, leading to thiazoline derivatives, the reaction of 1a with phenyl isothiocyanate at room temperature gives 5,5-dimethyl-3-phenyl-Δ¹-imidazolin-4-dimethyliminium-2-thiolate ( 9 , Scheme 2). The structure of 9 is deduced from spectral data and reactions of this zwitterionic compound (Schemes 2 and 4).     

Improved procedure for the preparation of 3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-3-ones

Treatment of 2,2-dimethyl-2H-1-benzopyrans 5 with a m-chloroperoxybenzoic acid-trifluoroacetic acid mixture and subsequent short path bulb to bulb vacuum distillation of the crude 3,4-hydroxyesters 6 formed afforded title compounds in good yields. Suppression of trifluoroacetic acid was required when using 2,2-di-methyl-2H-1-benzopyrans with electron donating substituents such as precocenes, as starting compounds.     

Additionsreaktionen von 3-Dimethylamino-2,2-dimethyl-2H-azirin an Isothiocyanate

Addition Reactions of 3-Dimethylamino-2, 2-dimethyl- 2 H-azirine and Isothiocyanates. The title azirine readily reacts with two molecules of benzyl- or methylisothiocyanate to form the zwitterionic 1:2 addition compounds 4 and 13 , respectively (Scheme 2). The presumed 1:1 addition products, which are intermediates in the formation of 4 and 13 , cannot be detected. The structure of 4 and 13 follows from their spectroscopic and chemical properties. With water they give the thiourea derivates 5 and 14 , respectively; treatment with aqueous acid leads to the Δ²-1, 3-thiazolin-5-on-derivates 7 and 15 , respectively. With sodium borohydride compounds 8 and 16 , respectively, are obtained (Scheme 2). The zwitterionic compounds 4 and 13 are able to react further with one molecule of the isothiocyanates to give, in high-yield, triazines 9 and 18 , respectively (Scheme 3). The structure of these compounds was again derived from their spectroscopic data. The mechanism for the formation of 9 and 18 is given in Scheme 3. Acid catalysed hydrolysis of 9 and 18 lead to the trithiocyanuric acid derivates 12 and 20 , and to the spiro compounds 11 and 19 , respectively (Sceme 6). Reaction of 4 with one molecule of phenylisocyanate gives triazine 10 (Scheme 5). According to the X-ray analysis of the methyl compound 18 , there are strong steric interactions in this molecule which are due to the side chain. This is demonstrated by the small distances between C(2) … C(13), N(7) … C(11), and C(8) … C(11) (Table 4). These steric interactions, in addition, cause widening of the bond angles N(1)? C(2)? N(7) and C(9)? N(10)? C(11) (Fig.2). Furthermore, the triazine ring is no longer planar. This deformation of the ring diminishes repulsion between the methyl groups C(13) and C(15).     

Reactions of regioisomeric 3,3-dimethyl- and 2,2-dimethyl-6-trifluoromethyl-2,3-dihydro-4-pyrones with N-nucleophiles

Reactions of 2,2-dimethyl-6-trifluoromethyl-2,3-dihydro-4-pyrone with ethylenediamine, hydrazine, or hydroxylamine yield 5-methyl-7-trifluoromethyl-2,3-dihydro-1H-1,4-diazepine, 3(5)-(2-hydroxy-2-methylpropyl)-5(3)-trifluoromethylpyrazole, and 5-hydroxy-3-(2-hydroxy-2-methylpropyl)-5-triflouromethyl-Δ², respectively. The same compounds were obtained from 2-amino-1,1,1-trifluoro-6-hydroxy-6-methylhept-2(Z)-en-4-one and 2-hydroxy-6, 6-dimethyl-2-trifluoromethyltetrahydro-4-pyrone.     

Structure of photochromic 1′-phenyl-3′,3′-dimethyl-11-nitrospiro (indoline-2,2′-[2H-1]naphthopyran)

Conclusions X-ray diffraction structural analysis was used to establish the structure of photochromic r-phenyl-3,3-dimethyl-11-nitrospiro (indoline-2,2-[2H-1]-naphthopyran) and showed that the (5-6)-fusion of an additional benzene ring in the spiropyran, in which an NO₂ group is located at C¹¹, leads to shortening of the C_spiro-0 bond to 1.460(2) å in comparison to an unfused analog, although this bond is longer than an ordinary C-O bond in six-membered heterocycles.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 188–190, January, 1987.     

Low-temperature heat capacities and thermodynamic properties of 2,2-dimethyl-1,3-propanediol

The molar heat capacities C _p,m of 2,2-dimethyl-1,3-propanediol were measured in the temperature range from 78 to 410 K by means of a small sample automated adiabatic calorimeter. A solid-solid and a solid-liquid phase transitions were found at T-314.304 and 402.402 K, respectively, from the experimental C _p-T curve. The molar enthalpies and entropies of these transitions were determined to be 14.78 kJ mol⁻¹, 47.01 J K⁻¹ mol⁻ for the solid-solid transition and 7.518 kJ mol⁻¹, 18.68 J K⁻¹ mol⁻¹ for the solid-liquid transition, respectively. The dependence of heat capacity on the temperature was fitted to the following polynomial equations with least square method. In the temperature range of 80 to 310 K, C _p,m/(J K⁻¹ mol⁻¹)=117.72+58.8022x+3.0964x ²+6.87363x ³−13.922x ⁴+9.8889x ⁵+16.195x ⁶; x=[(T/K)−195]/115. In the temperature range of 325 to 395 K, C _p,m/(J K⁻¹ mol⁻¹)=290.74+22.767x−0.6247x ²−0.8716x ³−4.0159x ⁴−0.2878x ⁵+1.7244x ⁶; x=[(T/K)−360]/35. The thermodynamic functions H _T−H _298.15 and S _T−S _298.15, were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The thermostability of the compound was further tested by DSC and TG measurements. The results were in agreement with those obtained by adiabatic calorimetry.     

Conformational analysis of 2,2-dimethyl-5-alkyl-1,3-dioxa-2-silacyclohexanes

Study of conformational isomerization of 2,2-dimethyl-5-alkyl-1,3-dioxa-2-silacyclohexanes using quantum-chemical HF/6-31G(d) and PBE/3z approximations showed that its route involves an equilibrium between the chair conformers with different orientation of substituent at C⁵ ring atom and proceeds through a transition state corresponding to the 2,5-twist conformation. Molecular dynamics method showed that at room temperature this conformation transforms into the equatorial or axial chair conformers through 1,4-twist or sofa forms. Based on the experimental and theoretical values of vicinal ¹H NMR coupling constants we determined quantitative conformational composition of the molecules of these compounds and the values of ??G ⁰ of the conformational equilibrium.     

1, 5, 6, 7-Tetrahydro-2H-[1,4]diazepin-5,7-dione aus Malonimiden und 3-Dimethylamino-2,2-dimethyl-2H-azirin

1, 5, 6, 7-Tetrahydro-2H-[1, 4]diazepin-5, 7-diones from Malonimides and 3-Dimethylamino-2, 2-dimethyl-2H-azirine Reaction of the aminoazirine 1 with malonimides of type 7 in 2-propanol at room temperature leads to the 1,4-diazepine derivatives of type 9 (Scheme 3). The structure of 6, 6-diethyl-3-dimethylamino-2,2-dimethyl-1,5,6, 7-tetrahydro-2H- [1,4] diazepin-5, 7-dione ( 9a ) has been proved by single crystal X-ray analysis (Chapter 4). Reduction of the 7-membered heterocycle 9a with sodium borohydride yields the perhydro-[1,4]diazepin-5, 7-dione 10 , while 9a in ethanol at 60° undergoes a ring contraction to the 4 H-imidazole derivative 11a (Scheme 4): Mechanisms of these two reactions are discussed in comparison with previously reported reactions (Chapter 5).     

Bentonitic earth catalyzed rearrangement of aryl 1,1-dimethylpropargyl ethers. Synthesis of 2,2-dimethyl-2H-1-benzopyrans

Mexican Bentonitic earth (Tonsil) catalyzed the Claisen rearrangement of aryl 1,1-dimethylpropargyl ethers under mild conditions to provide 2,2-dimethyl-2H-1-benzopyrans. The synthesis of encecalin 2f and desmethoxyencecalin 2i , two biologically active products among other natural products ( 2b, 2e ) was performed by this procedure.     

Ring-Transformationen bei der Umsetzung von 3-(Dimethylamino)-2,2-dimethyl-2H-azirin mit 1-substituierten Imidazolidin-2,4,5-trionen

Ring-Transformations in the Reaction of 3-(Dimethylamino)-2,2-dimethyl-2H-azirines with 1-Substituted Imidazolidine-2,4,5-triones Reaction of 1-substituted imidazolidine-2,4,5-triones ( = N-substituted parabanic acids; 2 ) and 3-(dimethylamino)-2,2-dimethyl-2H-azirine ( 1 ) in i-PrOH or MeCN at room temperature yields 5,6,7,7a-tetrahydro-3H-imidazo[3,4-a]imidazole-5,7-diones 3 (Scheme 1). By ¹⁵N-NMR studies, using (3-¹⁵N)- 2a , it has been shown that only N( 1 ) in (¹⁵N)- 3a is labelled and, hence, N(4) stems from 1 , e.g. the azirine reacts via cleavage of the N(1)=C(3) bond. In MeCN at room temperature, the azacyclols 3 rearrange slowly to give monocyclic 2H, 5H-imidazol-2-ones 4 (Scheme 3); the ¹⁵N-label in (¹⁵N)- 4a is in position 1. Both reactions proceed via deep-seated skeletal rearrangements, most probably via ring-expansion/ring-contraction processes.     

Additionsreaktionen von 3-Dimethylamino-2,2-dimethyl-2H-azirin an Phenylisocyanat und Diphenylketen

Addition Reaction of 3-Dimethylamino-2,2-dimethyl-2H-azirine with Phenylisocyanate and Diphenylketene 3-Dimethylamino-2,2-dimethyl-2H-azirine ( 1a ) reacts with carbon disulfide and isothiocyanates with splitting of the azirine N(1), C(3)-double bond to give dipolar, fivemembered heterocyclic 1:1 adducts. In some cases, these products can undergo secondary reactions to yield 1:2 and 1:3 adducts. In this paper it is shown that the reaction of 1a with phenylisocyanate also takes place by cleavage of the N(1), C(3)-bond, whereas with diphenylketene N(1), C(2)-splitting is observed. The reaction of 1a and phenylisocyanate in hexane at room temperature yields the 1:3 adduct 2 in addition to the trimeric isocyanate 3 (Scheme 1). A mechanism for the formation of 2 is given in Scheme 5. Hydrolysis experiments with the 1:3 adduct 2 , yielding the hydantoins 4–6 and the ureas 7 and 8 (Schemes 3 and 5), show that the formation of this adduct via the intermediates d , e and f is a reversible reaction. The aminoazirines 1a and 1b undergo an addition reaction with diphenylketene to give the 3-oxazolines 14 (Scheme 8), the structure of which has been established by spectral data and oxidative degradation of 14a to the 3-oxazolin-2-one 15 (R¹ ? R² ? CH₃, Scheme 9).     

2,2-diphenyl-2λ5-phospha-phenalenyl-und 2,2-dimethyl-2λ5-phospha-indenyl-lithium

From the reaction of 1,8-bis(bromomethyl)naphthalene with diphenyl(trimethylsilyl)phosphine a cyclic phosphonium salt IX is formed which can be rearranged with (CH₃)₃PCH₂ to yield the cyclic ylide X. Its metallation with t-butyllithium gives 2,2-diphenyl-2λ⁵-phospha-phenalenyl-lithium XI. The anion of XI cannot be seen as a delocalized phospha-phenalenyl π-system but rather as a phosphonium-bis-ylide similar to the diphenylphosphonium-bis-benzylide.From 1,2-bis(chloromethyl)benzene and (C₆H₅)₂PSi(CH₃)₃ or from 1,2-bis(chloromagnesiummethyl)benzene and CH₃PCl₂, followed by quaternization using CH₃Br, cyclic phosphonium salts (XII and XV, respectively) can also be obtained, which may again be rearranged to form the ylides XIII or XVI. XVI gives with (CH₃)₃CLi 2,2-dimethyl-2λ⁵-phospha-indenyl-lithium XVII, containing a dimethyl-phosphonium-bis-ylide anion (“isophosphindolyl-lithium”).     

One-pot synthesis of 6H-2,2a1,3-triazaaceanthrylen-6-ones and 6H-2,2a1,4-triazaaceanthrylen-6-ones via tandem cyclization strategies

Two operationally simple one-pot protocols have been developed for the synthesis of 6H-2,2a¹,3-triazaaceanthrylen-6-ones and 6H-2,2a¹,4-triazaaceanthrylen-6-ones. The first Pd-catalyzed tandem cyclization of imidazo[1,2-a]pyrimidines/imidazo[1,2-a]pyrazines with 2-chlorobenzaldehydes could proceed in aqueous medium under air, affording the desired products in moderate to good yields. The molecular structures of products 3i and 5b were confirmed by X-ray crystallographic analysis.     

Synthesis and nonchair conformations of 2,2-disubstituted 4,4-dimethyl-1, 3-dioxanes

The fundamental possibility of the synthesis of 2-substituted 1,3-dioxanes by reaction of 1,3-dioxanium perchlorates with organometallic compounds is demonstrated. A method for the synthesis of acyl derivatives of heterocycles was developed on the basis of these compounds. The existence of 2,2,4,4-substituted 1,3-dioxanes in the twist conformation was shown by ¹H NMR spectroscopy; the twist conformation is explained by the effect of nonbonded 1,3-syn-axial interactions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1172–1179, September, 1978.     

Synthesis of 2, 2 -dimethyl-1-p-tolyl-1-hydroxypropane and 2,2-dimethyl-1-p-tolyl-1-oxopropane

Conclusions 2,2-Dimethyl-1-p-tolyl-1-hydroxypropane and 2,2-dimethyl-1-p-tolyl-1-oxopropane were obtained for the first time.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 149–150, January, 1973.     

Synthesis and photochromism of Δ2,2′-BI-(2H-1,4-benzothiazine)

Δ^2,2′-Bi- (2H-1,4-benzothiazine) (4), the parent ring system of a group of amino-acid pigments (trichosiderins) from red hair and feathers, has been synthesized by a simple and novel method involving air oxidation of 2H-1,4-benzothiazine, generated in situ by treatment of 1-(o-aminophenylthio)-2,2-diethoxyethane (1). This procedure yields only the yellow trans-isomer 4, which in solution exhibits marked photochromism, being reversibly converted into the red unstable cis-form 5 on brief irradiation with sunlight.