SYNTHESE VON (2-MERCAPTOPHENYL)-METHANPHOSPHONSÄUREESTERN

Synthetically and structurally interesting N′-phosphoryl amidines were obtained by the reaction of lithiated alkyl phosphonates with N,N-dialkylcyanamide via an unprecedented migration of the phosphoryl group.

The cis-dichloro-meso-hexaethylporphodimethene−zirconium(IV) complex has been functionalized to the corresponding dialkyl derivatives [R = Me, PhCH2, Ph], 3−5, displaying a variety of migratory pathways. In the case of benzyl derivative 4, the spontaneous migration of the first benzyl to the ligand, 6, is followed by the second one, photochemically induced, thus forming a Zr−porphyrinogen complex, 7. The methyl derivative undergoes thermally induced methane elimination with the metalation of the meso ethyl chains, 8. Migration of both methyl groups has been observed in the reaction of 3 with ButNC, with the preliminary formation of η2-imine, rearranging to the corresponding enamine, 9.

The acyl complexes [Mo(COR1)(CO)2(PPh2H)(η-C5H5)] (R1 = Me or Et) have been prepared in high yield by the reaction of [MoR1(CO)3(η-C5H5)] with PPh2H. Deprotonation of the diphenylphosphine ligand with 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu) at –78 °C produced a phosphorus-centred anion which can be alkylated by treatment with R2I (R2 = Me or Et) to give the substituted phosphine acyl complexes [Mo(COR1)(CO)2(PPh2R2)(η-C5H5)], or acylated with R2COCl to produce acylphosphine acyl complexes [Mo(COR1)(CO)2(PPh2COR2)(η-C5H5)]. If the deprotonation is carried out at room temperature, however, migration of the metal acyl group to the phosphorus atom occurs to give the molybdenum-centred anion [Mo(CO)2(PPh2COR1)(η-C5H5)]–, which can in turn be alkylated with R2I to give the acylphosphine alkyl complexes [MoR2(CO)2(PPh2COR1)(η-C5H5)]. The metal-centred anion also undergoes typical reactions with H+ and chlorinated solvents to give [MoX(CO)2(PPh2COR1)(η-C5H5)] (X = H or Cl). Mechanistic studies showed that (i) on deprotonation of the related complex [MoMe(CO)2(PPh2H)(η-C5H5)] the methyl group does not undergo migration to phosphorus, and (ii) the reaction is largely intramolecular but with a measurable intermolecular component. A mechanism is therefore proposed involving nucleophilic attack on the acyl carbon atom by the anionic phosphido ligand. Full spectroscopic data for the new complexes are reported and interpreted, and the crystal structure of [Mo(COMe)(CO)2(PPh2COMe)(η-C5H5)] has been determined.

Silylation of the oxidized ligand in lead(II) bis(3,5-tert-butyl-1,2-quinone-(3,5-di-tert-butyl-2-hydroxy-1-phenyl)imine), Pb(ONOQ)2, with chlorosilanes RSiX2Cl (R = Me, Ph; X = Me, Ph, Cl) results in the tetracyclic, pentacoordinate silicon compounds (ON[R]O)SiX2 with a reduced, dianionic amine-bisphenolate ligand in which the methyl or phenyl group has migrated to nitrogen. Methyl migration is observed exclusively over phenyl migration, though phenyl migration is observed if no alkyl groups are present on silicon. Chlorotriphenylstannane reacts similarly, with migration of the phenyl group from tin to nitrogen. The five-coordinate products adopt a trigonal-bipyramidal geometry with long bonds to the apical amine donors (d(Si–N) = 2.3–2.9 Å). Chlorine occupies the other axial position in strong preference to methyl or phenyl, while methyl has a modest preference for the axial position in comparison to phenyl (8.7:1).

Nanosecond laser flash photolysis has been used to study the primary processes in the photochromic reaction of five O-acylic derivatives of 1-hydroxy-2-methoxyanthraquinone with methyl (I), tolyl (II), phenyl (III), ethoxyl (IV), and diethylamino (V) groups in the migrating acyl. The triplet−triplet absorption spectra of the reactive triplet states of quinones IV and V were detected, and the rate constants of the primary photochemical step were measured. The temperature dependence of the rate constants of acyl migration in the triplet states of quinones IV and V was studied, and the Arrhenius parameters were determined. The rate constants of thermal acyl migration and their Arrhenius parameters were measured for compounds I−V. It was found that migrant nature significantly influences the activation energy of both thermal and photochemical reactions of acyl migration. The activation energy of thermal migration increases from 37.9 ± 0.2 kJ/mol for compound I up to 66.5 ± 0.7 kJ/mol for compound V. The photochemical process is characterized by considerably lower values of the activation energy (15.9 ± 0.8 and 26.0 ± 1.7 kJ/mol for compounds IV and V, respectively). It was confirmed in the present work that photochemical migration of acyl groups is an adiabatic process occurring on the triplet potential energy surface.

Cyclic glucose 4,6-(ethyl phosphates) undergo ring-opening in dilute sodium methoxide to afford glucose 4-(ethyl methyl phosphates) as the kinetically favoured products. Ring-opening occurs with preponderant inversion of configuration. On storage in sodium methoxide glucose 4-(ethyl methyl phosphates) afford glucose 6-(ethyl methyl phosphates) with retention of configuration at phosphorus. The stereochemical results for the ring-opening and migration reactions are fully consistent with the intermediacy of trigonal bipyramidal intermediates, which break down by apical departure of the leaving group before pseudorotation or after simple pseudorotational sequences. The configurations at phosphorus of the glucose 4(R)- and 4(S)-, and 6(R)- and 6(S)-(ethyl methyl phosphates) are established by independent synthetic sequences.

The structure of the methyl tert-butyl ether (MTBE) radical cation and mechanism of its thermal and photochemical reactions in irradiated freons (CFCl3, CF2ClCFCl2, and CF3CCl3) were studied. Radical products of MTBE radiolysis in the liquid phase were investigated by the spin trapping technique. The quantum-chemical calculations of the structure of MTBE radical cations and products of their transformations were carried out by density functional theory (DFT) and abinitioMP2 methods. The primary MTBE radical cations are stabilized in dilute solutions in CFCl3and CF3CCl3. The ion–molecule reaction (proton transfer from the radical cation) was found to occur in concentrated solutions in CFCl3immediately during irradiation. The action of light (λ = 436 to 546 nm) at 77 K on the MTBE radical cation in CFCl3and CF3CCl3matrices results in intramolecular migration of the methyl group to yield the distonic radical cation (CH3)2.CO+(CH3)2. The primary MTBE radical cations undergo an irreversible transformation with methane elimination resulting in formation of the 2-methoxypropene radical cation .CH2=С+(СН3)ОСН3in CFCl3and CF3CCl3matrices in the temperature range 110–130 K. In the case of CF2ClCFCl2matrix, such a reaction occurs during irradiation at 77 K. Using the spin trapping technique, it was shown that the liquid-phase radiolysis of the neat ether resulted in the formation of fragmentation products (.CH3,CH3О., and t-BuO. radicals) from the primary radical cations, as well as the products of their rearrangements and ion–molecule reactions.

The two aromatic S-enynes HC≡CCH(OH)(C6H4)SCH2C(R)═CH2 (1a, R = Me; 1b, R = H) containing olefinic groups with and without an internal methyl substitutent and the O-enyne HC≡CCH(OH)CMe2CH2OCH2C(Me)═CH2 (1c) also with an internal methyl substituent on the olefinic group but with no aromatic group have been prepared. In the [Ru]Cl-induced ([Ru] = Cp(PPh)3Ru) reactions of 1a,c, the presence of the methyl group promotes cyclization reactions and their tandem cyclizations are further induced by MeOH. The reaction of 1a in CH2Cl2 gives the three products 2a–4a. Complex 2a, with a seven-membered thio ring bonded at Cβ of the vinylidene ligand, is formed via a C–C bond formation between two unsaturated groups in moderate yield. Complex 3a is formed via migration of PPh3 from the metal onto the terminal carbon of the alkynyl group followed by coordination of the S atom. The carbene complex 4a is formed by S addition to the internal carbon of the alkynyl group accompanied by migration of the allylic group from sulf...

The exposure of preadsorbed oxygen to monomethylamine or the coadsorption of a 2:1 monomethylamine (CH3NH2)/dioxygen mixture at a Cu(211) surface at room temperature results in the formation of a surface species characterised by C(1s) and N(1s) binding energies of 285.2 and 398.2 eV, respectively, with a calculated carbon to nitrogen ratio of 2:1. This species, which we assign to a chemisorbed dimethylamine ((CH3)2NHx(a)), is the only adsorbed product of the reaction and its formation must involve the breaking of a carbon–nitrogen bond and the intermolecular transfer of a methyl group.

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Oxidation–reduction exchange of 2-acylenolato and trimethylphosphane ligands between d 6 and d 8 complexes of nickel and cobalt

Marine carotenoids halocynthiaxanthin 2, mytiloxanthin 3 and crassostreaxanthin B 4 have characteristic structures, commonly possessing a monoacetylenic end group. The cyclopentyl end group of 3 is believed to be formed in nature from the epoxide end group of 5,6-epoxy carotenoids such as 2 (Chart 1, route a). It is also conceivable that 4 including a novel tetrasubstituted olefinic end group arises from epoxy carotenoids by the opening of the C-6-oxygen bond of the oxirane ring and the subsequent migration of the methyl group at the C-1 position (route b). We found that treatment of the epoxide 6a having a partial structure of epoxy carotenoids with Lewis acids gave the cyclopentyl ethyl ketone 9 possessing the same configuration as 3, and the acyclic tetrasubstituted olefinic methyl ketone 11 including a partial structure of 4 (Chart 2). It supported the proposed metabolic pathway of 5,6-epoxy carotenoids. Toward the biomimetic synthesis of 4, we examined the reaction of epoxides having several substituents at C-6 position with Lewis acids. Among these epoxides, an epoxide 60 was found to provide a tetrasubstituted compound 61 as a major product. This could be converted into an aldehyde 73 in 8 steps which was transformed into a compound 75 through the coupling reaction with vinyllithium 63. Then, the first total synthesis of 4 was accomplished via the double Wittig condensation of 75 with phosphonium salts 76 and 77.

Cyclization of 1‐(2‐aminophenyl)‐1‐phenyl‐ethylenes or 1‐(2‐aminophenyl)‐1‐phenyl‐propenes (II) by condensation with phosgene led to 4‐phenyl‐carbostyrils (III) or 2‐chloro‐4‐phenyl‐quinolines (IV). Similarly, thiophosgene afforded 4‐phenyl‐thiocarbostyril.Treatment of 1‐(2‐aminophenyl)‐2‐methyl‐1‐p‐tolyl‐propene (VII) with phosgene led to the corresponding isocyanate IX, which cyclized in the presence of aluminum chloride with loss of a methyl group to 3‐methyl‐4‐p‐tolyl‐carbostyril (III‐6). However, 1‐(2‐aminophenyl)‐2‐methyl‐1‐phenyl‐propene (VIII) treated with phosgene gave the isocyanate XI and 3‐phenyl‐3‐isopropenyloxindole (X). Cyclization of the isocyanate XI with aluminium chloride led simultaneously to 3‐methyl‐4‐phenyl‐carbostyril (XIV), and with migration of a methyl group to 3‐methylene‐4‐methyl‐4‐phenyl‐3. 4‐dihydro‐carbostyril (XV).

To investigate the effects of electron-donating and electron-withdrawing substituents upon the reaction of porphyrins with osmium tetraoxide, and the pinacol-pinacolone rearrangement of the resulting diols, a series of meso-substituted porphyrins were prepared by total synthesis. Porphyrins with electron-donating substitutents at the meso-positions gave vic-dihydroxychlorins in which the adjacent pyrrole subunit was predominantly oxidized. No such selectivity was observed in a porphyrin containing a methoxycarbonyl as the electron-withdrawing group, whereas a formyl substituent again resulted in oxidation at the pyrrole unit adjacent to the meso-substituent. Under pinacol-pinacolone conditions, vic-dihydroxy chlorins containing 4-methoxyphenyl or 3,5-dimethoxyphenyl groups at the meso-position showed preferential migration of the ethyl group over the methyl group to give 8-ketochlorins, whereas the diol with an n-heptyl substituent under similar reaction conditions gave both 7- and 8-ketochlorins. In contrast, the diol containing a meso-formyl substituent produced the corresponding 7-ketochlorin exclusively. These results indicate that it is not possible to predict the reactivity of meso-substituted porphyrins in the osmium tetraoxide reaction nor the general substituent migratory aptitudes in the pinacol-pinacolone rearrangement based on simple electronic arguments, most likely because many parameters (e.g., meso-beta-pyrrolic steric crowding and long-range electronic effects) ultimately determine the reactivity. The structural assignments of the porphyrin diols and the keto-analogues were confirmed by extensive (1)H NMR studies; some of the dihydroxychlorins and ketochlorins were found to display unusual features in their (1)H NMR spectra.

Metal‐free borylative cyclization of biphenyl‐embedded 1,3,5‐trien‐7‐ynes in the presence of simple and inexpensive BCl3 provided synthetically useful borylated building blocks. The outcome of the process depends on the reaction temperature, with borylated phenanthrenes obtained at 60 °C and phenanthrene‐fused borylated cyclobutanes formed at 0 °C. Based on DFT calculations, a mechanism for these novel transformations has been proposed, which involves an uncommon skeletal rearrangement, including migration of a methyl group and alkyne fragmentation, unprecedented in BCl3‐promoted cyclization reactions.