On the Reaction of α,α-Dichlorocarbenium Ions with Isocyanates

Trichlormethanes 4 react with two equivalents of n-alkyl isocyanates R²-NCO in the presence of SbCl₅ to furnish the 2,2-dichloro-5,6-dihydro-6-oxo2H-1,3,5-oxadiazinium salts ( 9 ). The structure of these heterocycles is confirmed by an X-ray analysis of 9d (R¹ = ClC = CCl₂, R² = Et). p-Tolyl isocyanate is Friedel-Crafts alkylated by 4b in the presence of SbCl₅. Subsequent ring closure affords the quinolinium salt 13 , which is hydrolyzed to give inter alia the quinolone 16 .     

Cationic polymerization of β-pinene with the AlCl3/SbCl3 binary catalyst: Comparison with α-pinene polymerization

The polymerization of β-pinene with the AlCl₃/SbCl₃ binary catalyst was investigated in toluene at −40°C and was compared with that of α-pinene. The polymerization of β-pinene with AlCl₃ alone was very rapid and retarded on addition of SbCl₃, in sharp contrast to that of α-pinene where added SbCl₃ remarkably accelerated it to give relatively high molecular weight oligomers. Attempted copolymerization of the two isomers with the binary catalyst, in turn, induced their parallel homopolymerizations, indicating that the copolymerization was difficult due to the large difference in reactivity. The homopolymerizations with AlCl₃/SbCl₃ were not seriously affected by a sterically hindered base, 2,6-di-tert-butyl-4-methylpyridine (DTBMP); the initiating species, therefore, would be different in nature from a proton. © 1996 John Wiley & Sons, Inc.     

Pyrolysis products of untreated and flame retardant-treated α-cellulose and levoglucosan

A typical gas chromatogram of the volatile pyrolysis products of untreated α-cellulose contains 39 peaks; however, mass spectral data indicate that at least 59 compounds, with molecular weights less than about 150, are present. A total of 37 compounds have been identified, 13 of which have not been previously reported. Most of the newly identified compounds contain a benzene ring, indicating that these compounds may be products of reactions between initial volatiles. A comparison of the products generated in the temperature range of 330°–440°C indicates that the formation of pyrolysis products is essential independent of temperature. Comparisons of the chromatograms obtained for untreated levoglucosan and cellulose indicate that most of the decomposition of cellulose probably forms levoglucosan which then decomposes to yield the observed pyrolysis products. In addition, the products of flame retardant-treated levoglucosan are essentially the same as those of cellulose with the same retardant treatment. This suggests that the retardants act on the levoglucosan formed in the decomposition of the cellulose rather than on the cellulose directly.     

Reaction of 3-methyl phenol with methyl α-eleostearate

The aromatic ring substitution reaction of 3-methyl phenol with methyl α-eleostearate under acidic conditions was carried out. The product was analyzed to find out if 3-methyl phenol was subjected to the ring substitution reaction with methyl α-eleostearate at its conjugated double bonds. Up to two molecules of 3-methyl phenol were addition-reacted with the conjugated triene of the eleostearyl group of methyl α-eleostearate. The 4-position of 3-methyl phenol was preferentially subjected to the cresol's ring substitution. When 3-methyl phenol was reacted with a relatively large amount of methyl α-eleostearate, the substitution reaction occurred at the 6- as well as 4-position of 3-methyl phenol, to yield a methyl α-eleostearate dimer having 3-methyl phenol units in its molecule. The above results were confirmed by infrared (IR), nuclear magnetic resonance (NMR), and high-speed liquid chromatographic (HLC) analyses, and the results of a previous paper connected with reaction of 3-methyl phenol were supported by the results of this paper.     

α-Methylierter Fencholen- und α-Campholenaldehyd – Synthese und Reaktionen

α-Methylated Fencholenic and α-Campholenic Aldehyde – Synthesis and Reactions The syntheses of α-methylated fencholenic ( 6a ) and α-campholenic aldehyde ( 6b ) via the corresponding azomethines ( 5 ) are reported. Aldol condensations of 6a, b with following reductions give the allylic alcohols ( 12–16 ) and hydrogenation the saturated alcohols ( 17–21 ) with strong woody odors, some of the allylic alcohols resembling that of sandal wood. Simple reduction or oxidation of 6a, b give the alcohols ( 24, 27 ), ethers ( 26 ), esters ( 23, 25, 28 ) and ketones ( 29 ) which have interesting woody odors with spicy, earthy and herbaceous notes.     

Reaction of the benzoyloxy radical with α-methylstyrene

Benzoyl peroxide labelled with carbon-14 and tritium has been used for study of the end-groups in copolymers of α-methylstyrene (MST) with methyl methacrylate, in particular determination of the relative numbers of benzoate and phenyl end-groups derived from the initiator. MST is found to be quite reactive towards the benzoyloxy radical. It is deduced that combination is the dominant mode of termination in the copolymerization, that transfer reactions are not important and that there is little abstraction of hydrogen from MST by the benzoyloxy radical.     

The Reaction of α,β-Unsaturated Ethyl Esters with Vinylmagnesium Chloride

While the reaction of linear α,β-unsaturated ethyl esters with vinylmagnesium chloride yields vinyl ketones as the main product, the reaction of substituted α,β-unsaturated ethyl esters yields triethylenic carbinols.     

On the Reaction of α-Chlorobenzylic Cations with Isocyanates

Isocyanates react as N-nucleophiles with α-chlorobenzylic cations ( 2 ) to give 1-oxoisoindolium salts ( 5 ). From the reaction of benzotrichlorides with SbCl₅ and isocyanates the extremely reactive hexachloroantimonates 5 with R² = Cl are isolated. Hydrolysis of these cyclic N-acyl iminium salts affords phthalimides 6 . Reaction of 5 k with dimethylcyanamide gives the 2-azoniaallene salt 13 . p-Tolyl isocyanate is Friedel-Crafts alkylated by p-chlorobenzotrichloride ( 1i ) in the presence of SbCl₅ to furnish the 1,3-oxadiazinium salt 7 , which is hydrolyzed to give the benzophenone 9 . With ethanol the acetals 10 and 11 are formed from 7 .     

Radiation-induced copolymerization of α,β,β-trifluoroacrylonitrile with α-olefin

Homopolymerization and copolymerization of α,β,β-trifluoroacrylonitrile (FAN) with γ-olefins were carried out in bulk by γ-ray irradiation at 25°C. FAN gives very small quantities of brown and greasy low molecular weight polymer. Cyano groups in FAN polymer were found to be readily hydrolyzed to acid amide groups in the atmosphere. FAN was found to copolymerize with ethylene, propylene, and isobutylene via a radical mechanism to form equimolar copolymers in a wide range of monomer compositions. The polymerization rate increases linearly with FAN fraction in the monomer mixture. These copolymers are also hydrolyzed in the atmosphere, and the hydrolysis proceeds with more difficulty for the copolymer with higher α-olefin. The reactivity ratios r₁ (FAN) and r₂ (α-olefin) were determined to be 0.01 and 0.12 for the FAN/ethylene copolymerization and 0.01 and 0.07 for the FAN/propylene copolymerization. These results confirm that an alternating copolymerization takes place in the FAN/α-olefin system.     

Kinetics and thermal analysis of copolymerization of m-isopropenyl–α,α′-dimethylbenzyl isocyanate with styrene

The copolymerizations of m-isopropenyl–α,α′-dimethylbenzyl isocyanate (m-TMI) with styrene (STY) was investigated. The weight conversion of the copolymerization reaction increased as the duration of copolymerization increased. The reaction temperature was maintained between 60 and 75°C. Molecular weights of the copolymers decreased with increasing molar fraction of m-TMI in the feed. This study obtained reactivity ratios, Alfrey–Price parameters, Mark–Houwink constant, characteristic ratio, thermal degradation activation energy, difference of reactive propagation activation energy, and intrinsic viscosity for the copolymers. The copolymers were characterized by using elemental analysis (EA), gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. The copolymer chains in solution were observed to have a high degree of stiffness and a lack of rotational freedom. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2763–2770, 1999     

Poly(α,α,α′,α′-tetrafluoro-p-xylylene)

Poly(α,α,α′,α′-tetrafluoro-p-xylylene) was prepared by the pyrolysis of cyclo-di-(α,α,α′,α′-tetrafluoro-p-xylylene) and by the pyrolysis of α,α′-bis(alkylsulfonyl)-α,α,α′,α′-tetrafluoro-p-xylene. The pyrolysis of α,α′-dibromo-α,α,α′,α′-tetrafluoro-p-xylylene also gave the polymer, but the method is less satisfactory. Poly(α,α,α′,α′-tetrafluoro-p-xylylene) shows remarkable thermal and oxidative stability at elevated temperatures. Useful mechanical and electrical properties are retained after aging for 3000 hr at 250° in air. After initial change due to crystallization, tensile strength remains near 10,000 psi, elongation above 5%, and dielectric constants and dissipation factors at approximately 2.4 and .001, respectively.     

Enantioselective Aza‐Morita–Baylis–Hillman Reaction Using Aliphatic α‐Amidosulfones as Imine Surrogates

The bifunctional catalyst 6′‐deoxy‐6′‐acylamino‐β‐isocupreidine ( 1 ) served both as a base to trigger the in situ generation of N‐sulfonylimine from readily available α‐amidosulfones and as a chiral nucleophile to initiate the enantioselective aza‐Morita–Baylis–Hillman (aza‐MBH) reaction. α‐Methylene‐β‐amino‐β‐alkyl carbonyl compounds, difficultly accessible previously, can now be synthesized in excellent yields and enantioselectivities.     

Highly Efficient Suzuki Coupling Reaction of α‐Chloroalkylidene‐β‐lactones and β‐Lactams with Organoboronic Acids

The activation of C Cl bond of (Z)‐α‐chloroalkylidene‐β‐lactones and (E)‐α‐chloroalkylidene‐β‐lactams via the Suzuki cross‐coupling reaction is reported in this paper. Alkyl, heteroaromatic, substituted phenyl‐ and alkenylboronic acids can be coupled with a wide variety of α‐chloroalkylidene‐β‐lactones and β‐lactams in excellent yields within a short period of time. The cross‐coupling reaction of optically active substrates leads to the optically active compounds without racemization of the corresponding chiral center.     

The Reaction of N-Bromoacetamide with α, β-Unsaturated Carbonyl Compounds. Part II

Transformation of some chalcone bromohydrins and their acetates under different conditions are described.     

Photochemistry of α,α′-Disubstituted Azoalkanes. I. Photosolvolytic Inversion and Substitution of α,α′-Dichloro- and α,α′-Dialkoyloxyazoalkanes

A series of α,α′-dichloro (α DClA), α,α′-dialkoyloxy- (αDAlA) and α,α′-dibenzoxy-azoalkanes (αDBeA) without α-aryl substituents was found to undergo meso ? dl photointerconversion upon direct irradiation through Pyrex in the presence of oxygen in a number of solvents. Furthermore, irradiation of α,α′-dipropionoxy-azoalkanes in benzene in the presence of excess acetic acid leads to substitution of the propionoxy groups by acetoxy groups in addition to meso ? dl photointerconversion. Similar irradiation in the presence of CH₃CO₂D does not lead to deuterium substitution of the β-hydrogens. The presence of benzenethiol radical scavenger does not affect the course of these photoreactions. Photosolvolysis schemes involving heterolysis (in the case of αDAlA and αDBeA) or an unstable intermediate (in the case of αDClA) are proposed.     

Oxygen‐Involved Oxidative Deacetylation of α‐Substituted β‐Acetyl Amides – Synthesis of α‐Keto Amides

α‐Substituted β‐acetyl amides could undergo C C bond cleavage to form α‐keto amides when treated with copper(II) chloride (CuCl₂) and boron trifluoride diethyl etherate (BF₃⋅OEt₂) under an oxygen atmosphere. The yield can be increased by the addition of tert‐butyl hydroperoxide which alone can also effect the reaction. The reaction provides a new protocol for the synthesis of α‐keto amides.

     

Enantioselective Construction of Cyclic Indolyl α‐Amino Esters via a Friedel–Crafts Alkylation Reaction

An enantioselective Friedel–Crafts alkylation reaction of indoles with cyclic N‐sulfonyl ketimino esters was developed. Under the optimized conditions using a chiral copper(II) triflate‐bisoxazoline complex as the catalyst, a range of N‐sulfonyl ketimino ester derivatives and indoles reacted smoothly to afford indole‐containing chiral cyclic α‐amino esters bearing tetrasubstituted α‐stereogenic centers [3‐ethoxycarbonyl‐3‐(3‐indolyl)‐2,3‐dihydrobenzo[d]isothiazole 1,1‐dioxides] in excellent yields and with high enantioselectivities (up to 99% ee). Pyrrole and N,N‐dimethylaniline were also investigated as aromatic substrates to afford the corresponding products with good results. An asymmetric induction model was then proposed on the basis of the observed absolute configuration of the product 3‐ethoxycarbonyl‐3‐(5‐bromo‐3‐indolyl)‐2,3‐dihydrobenzo[d]isothiazole 1,1‐dioxide. Synthetic transformations to convert the products into cyclic chiral N‐sulfonamido alcohols and the deprotection of the sulfonamides were performed. This study provides an efficient approach to chiral α‐tetrasubstituted indolic α‐amino acids as potential building blocks for peptides and biologically active molecules.

     

Synthesis of α, α′, β-trideuterovinyl acetate

Reaction conditions for the synthesis of α, α′, β-trideuterovinyl acetate by the continuous vapour phase catalytic reaction of deuteroacetylene and acetic acid-d (CH₃COOD) are described.