The insertion and extrusion of heterosulfur bridges. IX: Sulfur bridging in 2-phenylnaphthalene

Sulfur bridging of 2-phenylnaphlhalene ( 3 ) to form benzo[b ]naphtho[2,1-d]thiophene ( 5 ) (main product) and the isomeric benzo[b]naphtho[2,3-d]thiophene ( 4 ) is effected by means of hydrogen sulfide, benzene (solvent), and a sulfided cobaltous oxide-molybdic oxide-alumina (CMA-1) catalyst at 450–630° in a flow system (maximum yield 33% at 500°). The low yield is ascribed to decompositions of both 4 and 5 under reaction conditions.     

The insertion and extrusion of heterosulfur bridges. VIII. Dibenzothiophene from biphenyl and derivatives

Sulfur bridging of biphenyl ( 4 ), 4-methylbiphenyl, and the biphenylthiol isomers ( 7 ) to yield dibenzothiophene ( 3 ) is effected by means of hydrogen sulfide, benzene (solvent), and a sulfided cobaltous oxide-molybdic oxide-alumina (CMA-1) catalyst at 450° in a flow system. Alumina also catalyzes a number of these transformations. The possibility that compounds 7 (especially the 2-isomer) are intermediates in the conversion 4 → 3 is noted.     

The insertion and extrusion of heterosulfur bridges. III. A useful chemical-chromatographic separation procedure

A method is described for the isolation of pure phenanthro[4,5-bcd] thiophene ( 4 ) from a sulfur-bridging reaction mixture, also containing phenanthrene ( 3 ) and elemental sulfur, by selective oxidation of 4 to the sulfoxide ( 5 ) by means of iodobenzene dichloride, chromato-graphic separation of 5 on silica gel, and finally reduction of 5 back to 4 by means of sodium bis(methoxyethoxy)aluminum hydride in 25% overall yield from 3.     

The insertion and extrusion of heterosulfur bridges. VI. Comparative desulfurizations of dibenzothiophene and biphenylthiols

Products were determined from reaction of biphenyl-2-thiol ( 5 ) with methanol in a packed flow reactor at elevated temperatures and ca. atmospheric pressure. At 450–550° thermolysis of 5 gives small yields of dibenzothiophene ( 1 ) and biphenyl ( 2 ). With sulfided alumina, products vary with reaction temperature from 82% S-methyl- 5 at 250° to only 1 plus 2 at 550°. At 450° with sulfided cobaltous oxide-molybdic oxide-aluminum oxide (CMA-1), 5 and its isomers give mainly desulfurization to 2 (81%), plus C-melhylalion to melhylbiphenyls and fluorene. With CMA-1 at 450° the arrays of products from 1 and 5 are closely similar.     

The insertion and extrusion of heterosulfur bridges. X. Conversions in the triphenylene-triphenylo[4,5-bcd] thiophene system

Sulfur bridging of triphenylene ( 3 ) to form triphenylo[4,5-bcd]thiophene ( 4 ) is effected in 18% yield by means of hydrogen sulfide and a molybdena catalyst (CMA-1) at 500°. Compound 4 is purified through its sulfoxide, converted into its sulfone ( 6 ), and desulfurized (by means of CMA-1 plus methanol-benzene) back to 3 . The ultraviolet absorption spectrum of 4 resembles closely that of benzo[e]pyrene. On electron impact 4 shows little skeletal fragmentation, while 6 readily evolves sulfur monoxide and the formyl group.     

The insertion and extrusion of heterosulfur bridges. V. Desulfurization of dibenzothiophene by means of methanol and molybdena catalysts

Desuliurization of dibenzothiophene is effected in 82% yield by means of methanol and a sulfidcd cohaltous oxide-molylxlic oxide-aluminum oxide catalyst at 450° and ca. one atmosphere pressure in a flow system. The methanol serves as a hydrogen donor and methylating agent to form biphenyl (main product), 3- and 4-methylbiphenyls, and fluorene.     

The insertion and extrusion of heterosulfur bridges. XI. Desulfurizations of condensed thiophenes by means of methanol and a molybdena catalyst

Desulfurizations of 2-methyl- ( 1b ), 4-methyl- ( 1c ), and 4,6-dimethyldibenzothiophenes ( 1d ), benzo[b]thiophene ( 2 ), and benzo[b]naphtho[2,1-d]thiophene ( 5 ) were effected by means of methanol and a sulfided CMA catalyst [a mixed oxide of Co(II), Mo(VI), and Al(III)] at 450°. Desulfurization was accompanied by processes of demethylation and ring hydrogenation in the case of 1d and by both methylation and demethylation in the cases of 1b and 1c . Compound 2 gave ethylbenzene (80%), while 5 produced 2-phenylnaphthalene (69%).     

The insertion and extrusion of heterosulfur bridges. VII. Desulfurization of phenanthro[4,5-bcd]thiophene by means of methanol and a molybdena catalyst

Phenanthro[4,5-bcd]thiophene ( 1 ) is converted into phenanthrene ( 2 ) (50%) and a mixture of methylphenanthrenes ( 3 ) (12%) by means of methanol and a sulfided cobaltous oxide-molybdic oxide-aluminum oxide catalyst (CMA-1) at 450° in a flow system. Similarly, 2 gives 3 ; and 4-methylphenanthrene yields 2 plus 3 (main component 3-methylphenanthrene) under the same reaction conditions. Mechanisms of the reactions are discussed. A facile chromatographic separation for 1- and 4-keto-1,2,3,4-tetrahydrophenanthrenes is presented.     

The insertion and extrusion of heterosulfur bridges. XV. S-bridging of 2,2′-binaphthyl and 1-(2-naphthyl)cyclohexene. Studies on hydrodehalogenation during the reaction

Regioselectivity occurs in the sulfur-bridging reactions of 2,2′-binaphthyl (1) and 1-(2-naphthyl)cyclohexene (7) by means of hydrogen sulfide and a chromia-alumina-magnesia catalyst (designated I) in a flow apparatus at 550°. Thus, 1 gives a higher yield (6.1%) of dinaphtho[1,2–6:2′,l'-d]thiophene from 1,1′-bridging than of dinaphtho[1,2-b:2′,3′-d]thiophene (3.4%) from l,3′-bridging. No product expected from 3,3′-bridging was identified. Substrate 7 undergoes both dehydrogenation and bridging to yield 2-phenylnaphthalene (8%), benzo[b]naphtho[2,1-d]thiophene (9%) from alpha bridging, and benzo[b]naphtho[2,3-d]thiophene (3%) from beta bridging into the naphthalene ring. Exploratory studies showed that either sulfided catalyst I or a sulfided molybdenum( VI ) oxide-alumina-cobalt( II ) oxide catalyst ( II ) effects hydrodehalogenation of various monohalo- and polyhaloarenes (where halo, X, is chloro or bromo) at 450–550°. In the biphenyl, phenanthrene, naphthalene, and pyrene systems, halogen was lost either under sulfur-bridging conditions or under hydrogenolysis conditions, i.e. with methanol as a reactant. For every substrate the parent arene was isolated or identified as a reaction product. In selected experiments, acid HX was also identified in the effluent. Use of hydrogen sulfide as a reactant led to formation of dibenzothiophene and phenanthro[4,5-bcd]thiophene as main products in the biphenyl and phenanthrene systems, respectively; while use of methanol as a reactant gave small amounts of methyl bromide (for X = Br) and methylarenes.     

Selectivity in an asymmetric nitrogen insertion process

A simple and efficient synthesis of chiral lactams utilizing a group-selective nitrogen insertion process has been investigated for a group of prochiral ketones. The preparation of a useful intermediate in benzomorphinan synthesis has been carried out in optically active form.     

The purification process and side reactions in the N-methylmorpholine-N-oxide (NMMO) recovery system

In the lyocell process, N-methylmorpholine-N-oxide (NMMO) with a high recovery rate is used as a solvent to directly dissolve cellulose, which is of great significance for the realization of industrialization. In this paper, the impurity removal process and side reactions in the NMMO recovery system are introduced. The NMMO recovery system is generally composed of three major processes: air flotation, ion exchange and evaporation. Air flotation and ion exchange are the processes of removing impurities. And evaporation, where side reactions occur, is the process of increasing the concentration of NMMO. In terms of conductivity and colority, organic flocculants are better than inorganic flocculants in the air flotation process which mainly removes undissolved particulate matter, part of hemicelluloses and some colored substances. The ion exchange process mainly removes ionic substances and propyl gallate (PG). Side reactions occur during evaporation, producing colored substances and black particulate matter. Through analysis, it can be known that the production of colored substances is caused by the condensation reaction of N-methylmorpholine (NMM, 1), morpholine (M, 2), 2-Amino-4-methyl-oxazole (3), furfuryl alcohol (4), Morpholinoacetonitrile (5), xylose and NMMO under alkaline and high-temperature conditions, rather than by PG. The black particles are due to thermal degradation of NMMO or NMM or M in the presence of oxygen and iron at high temperatures.

     

Palladium(II) allylic complexes by carbene transmetalation and migratory insertion reactions: Synthesis and side reactions

New 1,1-alkoxy, aryl substituted palladium η³-allyls [Pd(μ-Br){η³-C(C₆F₅)(OMe)CHR¹CHR²}]₂ can be synthesized from [W(CO)₅{C(OMe)CHR¹CHR²}] and a palladium perfluoroaryl complex. The allyls are formed by transmetalation of the carbene fragment followed by migratory insertion of C₆F₅ to the putative and highly reactive Pd carbene complex. This reaction pathway predominates in all cases, but insertion of the double bond of the tungsten alkoxyvinylcarbenes into the Pd-C₆F₅ bond leads to secondary products, namely C₆F₅(OMe)CCR¹CH(C₆F₅)R².     

The terminations step in palladium-catalyzed insertion reactions

CH activation of several types of molecules, ranging from olefins and alkynes to non-activated aliphatic and aromatic compounds, is shown to occur with the same model system, involving a norbornylpalladium bond, stable towards hydrogen elimination, in the presence of suitable molecules or groups. Alternatively, hydrogen transfer can be observed if hydrogen donors are present and nucleophilic attack following insertion of CO.     

Reversible lithium insertion and copper extrusion in layered oxysulfides

All of the copper in the layered oxysulfides Sr2MnO2Cu1.5S2 and Sr2MnO2CU3.5S3 may be extruded as the element and the copper ions replaced quasi-reversibly by lithium ions in reductive topotactic ion exchange reactions; dramatic changes in magnetic properties result.     

Homolytic reactions of polyfluoroaromatic compounds. Part XII. Aryldehydrogenation and aryldefluorination in polyfluorobenzenes

The thermal decomposition of benzoyl peroxide in a range of polyfluorobenzenes at 80° gives biaryls arising from both the displacement of fluorine and hydrogen. Phenyldefluorination predominated only in the attack of 1,2,3,4-tetrafluorobenzene and of pentafluorobenzene, but was evident even in the attack of $\text{o}$-difluorobenzene. The relative rates of displacement, as shown by the isomer distributions, were generally well reflected by the application of partial rate factors found in the phenylation of fluorobenzene; however, phenyldefluorination was not so easily amenable to this treatment, a possible consequence of complex formation between radical precursor and substrate.     

Selectivity control in alkylidene carbene-mediated C-H insertion and allene formation

Regioselectivity of alkylidene carbene-mediated C-H insertion was explored utilizing electronic, conformational, steric, and stereoelectronic effects. Relying on these factors, highly regio- and chemoselective carbene insertion reaction of C-H bonds in different environments could be obtained. The observed selectivity clearly indicates that an electronic effect plays a more important role than steric effect. In general, C-H bonds in conformationally rigid cyclic environments are less reactive than those in acyclic systems toward carbene insertion, and in this situation, a competing intermolecular reaction between alkylidene carbene and trimethylsilyldiazomethane led to the formation of allenylsilanes. The formation of allenylsilane becomes more favorable as the concentration of reaction becomes higher, as well as the C-H bonds undergoing insertion becomes electronically and conformationally deactivated.