Photoinitiated processes in 1-p-tolylsulfonylazo-2,4,6,8-tetrakis(tert-butyl)phenoxazine

New photochromic compound 1-p-tolylsulfonylazo-2,4,6,8-tetrakis(tert-butyl)phenoxazine containing the intramolecular hydrogen bond NH...N and the corresponding model structures 2,4,6,8-tetrakis(tert-butyl)-1-(veratroylazo)phenoxazine and 2,4,6,8-tetrakis(tert-butyl)-N-acetyl-1-(p-tolylsulfonylazo)phenoxazine were synthesized and studied. The data obtained suggested the mechanism of the photoreaction resulting in the accumulation of betaine 1-hydroxy-2,4,6,8-tetrakis(tert-butyl)-10-tolylsulfonylphenoxazin-9-one. The photochromic transformations in the molecule under study are due to intramolecular proton phototransfer followed by E–Z-isomerization about the N–N bond and the formation of betaine 1-hydroxy-2,4,6,8-tetrakis(tert-butyl)-10-tolylsulfonylphenoxazin-9-one. The molecular and crystal structure of the photoproduct was studied by X-ray analysis.     

Synthesis,chemical properties,and crystal structure of 2,4,6,8-tetra(<Emphasis Type="Italic">tert</Emphasis>-butyl)-9-hydroxyphenoxazin-1-one

The reaction of di(tert-butyl) derivatives of pyrocatechol with 2,6-dihydroxyaniline afforded 2,4,6,8-tetra(tert-butyl)-9-hydroxyphenoxazin-1-one. The chemical properties of the reaction product and its ability to form complexes with metal salts as the tridentate ligand were investigated. The structure of hydroxyphenoxazinone was established by X-ray diffraction.     

Synthesis and structure of 2,4,6,8-tetramethyl-3,7-dithia-2,4,6,8-tetraazabicyclo[3.3.0]octane 3,3,7,7-tetraoxide

Condensation of N,N′-dimethylsulfamide with glyoxal gave 2,4,6,8-tetramethyl-3,7-dithia-2,4,6,8-tetraazabicyclo[3.3.0]octane 3,3,7,7-tetraoxide, a sulfur-containing analog of 2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione (Mebicar). The product structure was studied by X-ray analysis.     

A novel and efficient synthesis of pyrimido[4,5-d]pyrimidine-2,4,7-trione and pyrido[2,3-d:6,5-d] dipyrimidine-2,4,6,8-tetrone derivatives

An efficient and direct procedure for the synthesis of pyrimido[4,5-d]pyrimidine-2,4,7-trione derivatives has been described under microwave-assisted conditions. Reaction of 6-amino-1,3-dimethyluracil with aromatic aldehydes resulted in the formation of pyrido[2,3-d:6,5-d] dipyrimidine-2,4,6,8-tetrone derivatives.     

Synthesis of 2,4,6,8-Tetrasubstituted 1,5-Naphthoquinones

Derivatives of N-aryl-5-hydroxy-1,4-naphthoquinone 4-imines react with primary amines to afford 2,4,6,8-tetrasubstituted 1,5-naphthoquinones.     

Structure and magnetic properties of 2,4,6,8-tetra(<Emphasis Type="Italic">tert</Emphasis>-butyl)phenoxazin-1-one adducts with cobalt(II) salts

Complex formation reaction of redox-active 2,4,6,8-tetra(tert-butyl)phenoxazin-1-one with cobalt(II) chloride leading to the dimeric adduct has been studied. UV spectroscopy studies have revealed the equilibrium of the formed adduct with dissociated form of the complex in the acetonitrile solution. In the presence of ethylene glycol, the complex formation with cobalt(II) perchlorate has afforded the high-spin trimolecular adduct. Crystal structure of the obtained adducts has been studied by means of X-ray diffraction analysis.     

Struktur von S-9,10-Dimethyl-1,3,5,7-tetraarsa-2,4,6,8-tetraoxaadamantan und 9,10-Diethyl-1,3,5,7-tetraarsa-2,4,6,8-tetraoxaadamantan

Structure of S-9,10-Dimethyl-1,3,5,7-tetraarsa-2,4,6,8-tetraoxaadamantane and 9,10-Diethyl-1,3,5,7-tetraarsa-2,4,6,8-tetraoxaadamantane S-9,10-Dimethyl-1,3,5,7-tetraarsa-2,4,6,8-tetraoxaadamantane ( 1 ) and 9,10-diethyl-1,3,5,7-tetraarsa-2,4,6,8-tetraoxaadamantane ( 2 ) have been prepared by the reaction of propionic acid, propionic anhydride and butyric acid, butyric anhydride, respectively, with arsenic(III)-oxide. The crystals of 1 are rhombic, a = 6.902(4), b = 11.121(5), c = 13.988(8), space group P2₁2₁2₁. The crystals of 2 are monoclinic, a = 11.757(10), b = 11.255(10), c = 18.631 (18), β = 91.78(7), space group P2₁/n. The mean bond lengths and angles in 1 are AsO = 1.790 Å, AsC = 1.959 Å, OAsO = 100.60°, CAsO = 99.65°, AsOAs = 128.77°, AsCAs = 118.73°, and in 2 they are AsO = 1.780 Å, AsC = 1.978 Å, OAsO = 101.45°, CAsO = 99.55°, AsOAs = 129.64°, AsCAs = 117.72°.     

Stereochemistry of the reaction of cis,trans,cis-2,4,6,8-tetraisocyanato-2,4,6,8-tetramethylcyclotetrasiloxane with triphenylsilanol and 1,1,3,3-tetraphenyldisiloxane-1,3-diol

All-cis-2,4,6,8-tetramethyl-2,4,6,8-tetrakis(triphenylsiloxy)cyclotetrasiloxane (4) and syn-1,3,9,11-tetramethyl-5,5,7,7,13,13,15,15-octaphenyltricyclo[9.5.1.1^3,9]octasiloxane (5) were synthesized by the reaction of cis,trans,cis-[MeSi(NCO)O]₄ (1) with Ph₃SiOH (2) and [Ph₂Si(OH)]₂O (3), respectively, in the presence of pyridine for the sake of investigating the synthesis of ladder polysilsesquioxanes with perfect siloxane frameworks. Their stereostructures were confirmed by nuclear magnetic resonance spectra and X-ray crystallography, which revealed that 4 and 5 did not retain the stereostructure of the precursor 1. This result was caused by the racemization of 1 with pyridine, and a subsequent nucleophilic substitution reaction of 1 with 2 or 3, including inversion and retention of the configuration at the silicon atoms.     

Bis (2,4,6,8-cyclononatetraen-1-yl)methane

Bis (2,4,6,8-cyclononatetraen-1-yl)methanes Bis (2,4,6,8-cyclononatetraen-1-yl)methanes ( 2a–c ) have been prepared by reaction of all-cis-cyclononatetraenide with 1,1-dichlorodimethyl ether as well as with carbenium ion precursors 9b and 9c . The title compounds 2 are attractive precursors of highly delocalised nonafulvenes of type 3 ; however, elimination experiments 2→3 failed so far.     

Synthesis of ethyl 2-aminodihydro-5-pyrimidinecar-boxylate derivatives and 3,7-diethoxycarbonyl-4,6-dihydro-2,4,6,8-tetraaryl-1H-pyrimido[1,2-a]pyrimidines

Reactions of ethyl 3-aryl-2-benzoylpropenoates 1 with guanidine and N-alkyl(or benzyl)guanidines have been investigated. Ethyl 2-aminodihydro-5-pyrimidinecarboxylate derivatives 3, 4 or 5, and 3,7-diethoxy-carbonyl-4,6-dihydro-2,4,6,8-tetraaryl-1H-pyrimido[1,2-a]pyrimidines 6 have been synthesized.     

N-Silylation of 2,4,6-Trialkyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-diones

N-Trimethylsilyl derivatives of 2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-diones have been prepared for the first time and the electrophilic substitution reaction of the trimethylsilyl group has been studied.     

Pyrimidines. LII Synthesis of pyrido[2,3-d]pyrimidine-2,4-diones and pyrido[2,3-d:6,5-d']dipyrimidine-2,4,6,8-tetrones

Reactivities of 5-dimethylaminomethylene-6-imino-1,3-dimethyluracil hydrochloride ( 1 ) toward a variety of active methylene compounds 2 and 5 were investigated. Treatment of 1 with active methylene compounds such as malononitrile and ethyl cyanoacetate in the presence of triethylamine gave pyrido[2,3-d]pyrimidine-2,4-dione derivatives 3. Reaction of 1 with barbituric acids resulted in the formation of pyrido[2,3-d:6,5-d′]di-pyrimidine-2,4,6,8-tetrone derivatives 6.     

Synthesis of 2-monofunctionalized 2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-diones

New (1R*,5S*)-2-R-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-diones containing the terminal carboxy or hydroxy group in the substituent R were synthesized by cyclocondensation of 4,5-dihydroxyimidazolidin-2-one with 1-R-ureas. Single-crystal X-ray diffraction analysis showed that 2-carboxyethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione crystallizes as a racemate.     

Polyene spectroscopy: Vibronic evidence for a forbidden transition in DECA-2,4,6,8-tetraene

The dimethylpolyene deca-2,4,6,8-tetraene was studied by absorption, fluorescence excitation and fluorescence spectroscopy in glasses at 77 K and in n-alkane crystals at 4.2 K. A strong transition to a ¹B_u excited state is observed with an origin at 32400 cm^?1 in isopentane at 77 K and at 31280 cm^?1 in n-undecane at 4.2 K. A weak transition to a ¹A_g excited state is observed with an origin at 28738 cm^?1 in the n-undecane matrix. The radiative fluorescence lifetime is 500 ns. In undecane the transition from the ground state to the ¹A_g excited state exhibits a classic Herzberg—Teller vibronic pattern indicating a symmetry forbidden transition.     

2,4,6,8-Tetraazabarbaralanes: Models for tetraazasemibullvalenes

3,7-Diethoxy-1,5-dimethyl-2,4,6,8-tetraaza-bicyclo[3.3.1]nona-2,6-diene (7), readily obtained from the corresponding urea derivative, can be oxidized to afford 3,7-diethoxy-1,5- dimethyl-2,4,6,8-tetraazabarbaralane (9) whose crystal structure corresponds to a localized molecule. On heating, 9 gives rise to 2-ethoxy-4,6-dimethyl-pyrimidine.     

Influence of conformational structure on the vibrational spectra of the different isomers of 2,4,6,8-tetraphenylnonane,a polystyrene model molecule

The influence of the chain configurations and conformations on the infrared and Raman spectra of 2,4,6,8-tetraphenylnonane has been investigated. The out-of-plane, skeletal, 16b and 10b normal modes of the benzene rings, and the methyl rocking are particularly sensitive to conformational effect. The results permit evaluation of the trans-trans defect ratio in isotactic crystalline polystyrene and suggest that atactic polystyrene is better described by prevailing syndiotactic sequences of at least eight aliphatic bonds in the trans conformation.     

Synthesis and separation of stereoisomeric 2,4,6,8-tetrasubstituted 3,7-dithia-1,5-diazabicyclo[3.3.0]octanes

Heterocyclization of hydrazine with aldehydes R-CHO (R = Me, Et, Prⁿ, Buⁿ, n-C₅H₁₁, Ph, 4-MeOC₆H₄, 3-Py) and H₂S leads to stereoisomeric 2,4,6,8-tetrasubstituted 3,7-dithia-1,5-diazabicyclo[3.3.0]octanes, which were separated by column chromatography. The trans-transoid-trans-configuration of tetramethyl(-ethyl,-propyl)-3,7-dithia-1,5-diazabicyclo-[3.3.0]octanes was inferred from the X-ray diffraction and ¹H and ¹³C NMR spectroscopic data.     

Stable axial-rich chair conformer of myo-inositol derivatives due to introduction of two adjacent bulky silyl protections

The ring-conformational change of myo-inositol derivatives by introducing two tert-butyldimethylsilyl, triisopropylsilyl, or tert-butyldiphenylsilyl groups into the 1,2-trans hydroxy groups--3,4- and 4,5-positions--were investigated. The cyclohexane cores of the 4,5-bis-O-silylated derivatives with tert-butyldiphenylsilyl or triisopropylsilyl groups were present in the axial-rich chair form.     

Syntheses of sulfoxide derivatives in the benzodiazine series. Diazines. Part 37

Syntheses of new sulfinylcinnolines, quinoxalines, quinazolines and phtalazines have been investigated starting from the appropriate halogenobenzodiazine derivatives. The latter were converted in one step to the corresponding sulfanyl benzodiazines which upon oxidation with m-CPBA led to the corresponding sulfoxide derivatives of benzodiazines in moderate to good yields. In parallel to this study, an improved method for the synthesis of 2-methylsulfinylquinoxaline starting from 2-sulfanylquinoxaline is also described and in the quinazoline series a synthetic route has been developed to prepare 2-tert-butyl-5-phenylsulfinylquinazoline with satisfactory yield as well as 2-tert-butyl-5-tert-butylsulfinyl-4(3H)-quinazolinone and 2-tert-butyl-8-tert-butylsulfinyl-4(3H)-quinazolinone.