Esters of alternating copolymers of maleic or 2,3-dimethylmaleic anhydride with alkyl vinyl ethers

Maleic anhydride or 2,3-dimethylmaleic anhydride was copolymerized with a number of alkyl vinyl ethers, with AIBN as the initiator. The comonomers were always alternating and were obtained in yields ranging from 15 to 99%. The acid anhydride group in both series of copolymers was converted to the corresponding methyl esters in a two-step reaction. The structure of these polymers was established by elemental analysis and by infrared, ¹H-and ¹³C-NMR spectroscopy. Addtional characterization of these copolymers were carried out by viscosity measurements, differential scanning calorimetry for the determination of glass transition temperatures, and thermal degradation for the determination of the thermal stability of the copolymers.     

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.     

Photoaddition of N-ethylmaleimide to cumene

The photoaddition of N-ethylmaleimide (NEMI) to cumene is compared with that of benzene. The equilibrium constants of the CT-complexes were determined by means of ¹H-N.M.R. spectroscopy (K_benzene-NEMI = 0.035 kg mole^?1, K_cumene-NEMI = 0.049 kg mole). By irradiation with light of wavelength 254 nm the 2:1 adduct cumene-NEMI is formed. The structure was determined by ¹ H-N.M.R. and mass spectrometry. These data indicate that only one of the possible isomers is formed and that the free rotation of the isopropyl group is hindered in the adduct. Furthermore two isomeric 1 : 1 adducts could be detected and assigned to the 1 : 1 cycloaddition product and to cumyl-N-ethyl-succinimide.     

Photoaddition of Ethyl 2,2-Dimethyl-5-oxo-5,6-dihydro-2H-pyridine-1-carboxylate to 2,3-dimethylbut-2-ene

On irradiation (350 nm) in the presence of excess 2,3-dimethylbut-2-ene, the newly synthesized title compound 5 affords as main products the unexpected cyclopropylpyrrolidine 10 (50%) and the spiro-oxetane 9 (25%).     

Photoaddition of Iodoform to P-Chlorostyrene and Indene

A new type of triiodo compounds synthesized by irradiation of p-chlorostyrene or indene with iodoform in the inert solvent is reported.     

Reaction of 2,3-diphenylpyrazine 1-oxides with acetic anhydride

Some 2,3-diphenylpyrazine 1-oxides were heated with acetic anhydride to give the corresponding 2,3-di-acetoxy-2,3-dihydro-5,6-diphenylpyrazines. By X-ray diffraction analysis, the configuration of two acetoxyl groups was determined to be trans.     

Photoaddition to DNA by Nonintercalated Chlorpromazine Molecules

Chlorpromazine (CPZ) forms photoadducts with DNA and photosensitizes DNA strand breaks. These reactions may be responsible for the reported photomutagenicity of CPZ and for the well-known cutaneous and ocular phototoxicity associated with this drug. We have investigated whether CPZ molecules that are intercalated between base pairs in double-stranded (ds) DNA are the absorbing species for the photoaddition reaction. Quenching of CPZ fluorescence by ds-DNA gave nonlinear Stern-Volmer plots, indicating that more than one type of complex is formed. Linear dichroism spectra of CPZ in the presence of ds-DNA showed a minimum at 345 nm, indicating that the absorption maxima of intercalation complex(es) are red-shifted compared to the absorption maximum of free CPZ at 307 nm. The sum of the absorption of all CPZ complexes with ds-DNA, obtained from dialysis experiments, was broadened and maximized at about 315 nm, indicating that complexes not involving intercalation dominate the absorption spectrum at X < 350 nm. The wavelength dependence for covalent binding of CPZ to DNA was determined by irradiating ³H-CPZ in the presence of ds-DNA at 310, 322, 334, 346, 358 and 370 nm. The resulting spectrum correlated closely with the absorption spectrum of nonintercalated CPZ rather than with the spectrum of intercalated CPZ, indicating that the latter species is not the chromophore for the photoaddition reaction.     

Cycloaddition reactions of 2,3-didehydrothiophene generated by flow vacuum thermolysis of thiophene-2,3-dicarboxylic anhydride

Flow vacuum thermolysis (FVT) of thiophene-2,3-dicarboxylic anhydride ($\text{2}$) in the presence of 2,3-dimethylbutadiene ($\text{6}$) gives, in addition to 5,6-dimethylthianaphthene ($\text{9}$). small quantities of a dihydrodimethylthianaphthene ($\text{12}$) and another dimethylthianaphthene ($\text{13}$) which is probably also formed by dehydrogenation of $\text{12}$ with chloranil. The partial structures of these minor products are consistent with their being formed by a [2+2]-cycloaddition between $\text{6}$ and an intermediate aryne, 2,3-didehydrothiophene ($\text{1}$), followed by a rearrangement of the resulting adduct $\text{11}$ and dehydrogenation. FVT of $\text{2}$ in the presence of 2,5- ($\text{17b}$) or 3,4-dimethylthiophene ($\text{17c}$) also gave a mixture of the dimethylthianaphthenes ($\text{18}$$\text{22}$, $\text{23}$) which can be rationalized as arising by a [4+2]- and two [2+2]-cycloadditions of the aryne $\text{1}$ to the thiophenes $\text{17}$ with subsequent desulfurization. The lack of equilibration of the products $\text{18}$, $\text{22}$ and $\text{23}$, was demonstrated and their origin as a function of the structure and reactivity of the aryne $\text{1}$ discussed.     

Tracing the Photoaddition of Pharmaceutical Psoralens to DNA

The psoralens 8-methoxypsoralen (8-MOP), 4,5′,8-trimethylpsoralen (TMP) and 5-methoxypsoralen (5-MOP) find clinical application in PUVA (psoralen + UVA) therapy. PUVA treats skin diseases like psoriasis and atopic eczema. Psoralens target the DNA of cells. Upon photo-excitation psoralens bind to the DNA base thymine. This photo-binding was studied using steady-state UV/Vis and IR spectroscopy as well as nanosecond transient UV/Vis absorption. The experiments show that the photo-addition of 8-MOP and TMP involve the psoralen triplet state and a biradical intermediate. 5-MOP forms a structurally different photo-product. Its formation could not be traced by the present spectroscopic technique.     

Photoaddition of maleic anhydride to unsaturated polymers in homogeneous solution,solid polymer–solution,and solid polymer–vapor systems

Photoreactions of maleic anhydride (MAH) with unsaturated olefinic polymers such as 1,2-polybutadiene, 1,4-polybutadiene, block copolymer of styrene and butadiene, polystyrene, poly(styrene-co-isoprene), and poly(styrene-alt-methyl methacrylate) were investigated in air. When the polymers have olefinic unsaturation, the addition of MAH to the polymers in homogeneous solutions proceeded efficiently by a chain mechanism, and the quantum yield of the photoaddition of MAH was greater than unity under irradiation at λ > 310 nm. From the effects of solvent and photosensitizer, a radical chain mechanism involving crosslinking of the polymers by MAH molecules was suggested. Together with the spectroscopic results, the reaction mechanism was discussed. The photoaddition reaction was then applied to the surface photomodification of polymer films. Photoreactions were conducted at the interphase between solid polymer and acetone solution of MAH and also at the interphase between solid polymer and gaseous MAH. Irradiation by a 300-W high-pressure mercury lamp could bring about considerable modification of the surface properties of the polymers, which then show improved wettability and dyeability. From the oxygen permeation experiments, the present interfacial phototreatment was shown to provide a double-layered polymer film in which one side of the film is polar and hydrophilic while the other side is nonpolar and hydrophobic.     

Photoaddition of Iodoform with Norbornene

The reaction of norbornene with iodoform in the inert solvent under irradiation resulted in Kharasch type addition to give endo-3-iodo-exo-2-diiodomethyl-bicyclo[2.2.1]heptane, and a carbene addition to give tricyclic compound, anti-3-iodo-exo-tricyclo[3.2.1.0^2,4]octane. The structural assignments of these adducts are based on elemental analyses, ir, nmr, and mass spectral studies.     

Photoaddition reactions of acetylene and butadiyne derivatives to benzodithiophene

The photochemical [2pi +2pi] cycloaddition of dimethyl acetylenedicarboxylate to benzo[1,2-b:4,5-b']dithiophene has been used to synthesize substituted cyclobuta[b]thieno[2,3-f][1]benzothiophene. The first [2pi + 2pi] photocycloaddition reaction of a series of butadiynes to benzodithiophene is reported to yield regioselective and acetylene-substituted cyclobutene derivatives containing an aromatic thiophene moiety.