Rhodium-catalyzed kinetic resolution of tertiary homoallyl alcohols via stereoselective carbon-carbon bond cleavage

A nonenzymatic kinetic resolution of tertiary homoallyl alcohols has been developed through a rhodium-catalyzed retro-allylation reaction under simple conditions. Selectivity factors of up to 12 have been achieved by employing (R)-H8-binap as the ligand, and the reaction can be conducted on a preparative scale.     

Rapid cleavage of the naphthylmethyl-oxygen bond in higher triplet excited states

Rapid cleavage of the naphthylmethyl-oxygen bond of 1- and 2-[(4-benzoylphenoxy)methyl]naphthalenes in higher triplet excited states occurred within a laser flash of 5 ns to give 1- and 2-naphthylmethyl radicals with formation quantum yields of 0.042 +/- 0.004 and 0.020 +/- 0.002, respectively, during two-colour two-laser flash photolysis.     

Kinetic data on the interaction between triplet anthraquinone and 2-naphthol in oxygen

During the photooxidation of ethylbenzene in the presence of 2-naphthol a new interaction has been found between the sensitizer anthraquinone and the inhibitor. The quantum yield and the kinetics of this interaction have been investigated in the temperature interval of 28–98°C.

---

-, , 28–98°C , .

     

Hydrogen bond formation between aliphatic alcohols and tertiary amines

Hydrogen bond formation between tertiary amines and long chain and branched chain alcohols has been studied in order to understand the influence of chain length and the steric effect on the complex formation between tertiary amines and alcohols. On the addition of the amine to the alcohol the intensity of the monomeric OH band decreases and the new band appears corresponding to the alcohol—amine complex. The equilibrium constants of the complex formation are correlated by a two parameter equation. The three correlation equations obtained for three tertiary amines are: log K = 3.41 + 10.01σ* + 0.02χ (for triethylamine-alcohol) log K = 0.97 + 2.54σ* + 0.21χ (for tributylamine-alcohol) log K = 1.01 + 1.81σ* + 0.26χ (for trioctylamine-alcohol), where σ* is Taft's polar constant and χ the molecular connectivity index of the R skeleton of the alcohol.     

Titanocene and zirconocene σ-alkynyl complexes in C---C single bond coupling and cleavage reactions

Group 4 metallocene mono- and bis-σ-alkynyl complexes of the type L₂M(σ-CCR) and L₂M(σ-CCR)₂ with M=titanium and zirconium in the oxidation states +3 and +4 and L=Cp (η⁵-cyclopentadienyl) and Cp^* (η⁵-pentamethylcyclopentadienyl) are important compounds for stoichiometric and catalytic C---C single bond coupling and cleavage reactions. Detailed investigations show five-membered metallacyclocumulenes L₂M(η⁴-1,2,3,4-RC₄R) as the key intermediates in both reactions of a C---C single bond cleavage of different 1,4-substituted 1,3-butadiynes RCC---CCR to alkynyl groups and the opposite reaction of C---C single bond formation starting from alkynyl groups under the formation of 1,4-substituted 1,3-butadiynes. Depending on different metals M and ligands L, coupling or cleavage is favoured. Combination of both reactions offered the first C---C single bond metathesis in homogeneous solution, which is photocatalyzed and titanocene-mediated. It proceeds via titanocene–mono-alkynyl complexes, which are interesting species also for other stoichiometric and catalytic C---C coupling reactions. Some similarities regarding the σ-to-π conversion exist between the coupling of the alkynyl groups at titano- and zirconocenes to complexed 1,3-butadiynes on one side and the coupling of phenyl groups at chromium to complexed diphenyl on the other side.     

Reaction of tertiary diacetylenic alcohols with amino alcohols

Conclusions It was shown that nitrogen-containing ethynyl vinyl ethers can be synthesized from tertiary diacetylenic alcohols and amino alcohols in the presence of alkaline catalysts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2604–2605, November, 1970.     

Photochemical transformations of anthraquinone in polymeric alcohols

It is established that the photolysis of anthraquinone in both aerated and deoxygenated polymeric alcohols is not accompanied by reduction with the formation of anthrahydroquinone; as a result, an adduct of hydroxyanthracene and polymeric alcohol is formed.     

Oxidative cleavage of tertiary cyclic alcohols by Pb(OAc)4-KSCN system

Conclusions Oxoalkyl radicals are generated by the reaction of 1-alkylcycloalkanols (ring size C₅-C₇) with the Pb(OAc)₄-KSCN system, which are oxidized by the ligand transfer mechanism to give oxoalkyl thiocyanates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1140–1142, May, 1979.     

Acyl iodides in organic synthesis: XI. Unusual N-C bond cleavage in tertiary amines

Acyl iodides reacted with excess primary and secondary amines in a way similar to acyl chlorides, yielding the corresponding carboxylic acid amide and initial amine hydroiodide. Reactions of tertiary amines with acyl iodides were accompanied by cleavage of the N-C bond with formation of the corresponding N,N-di(hydrocarbyl)carboxamide and alkyl iodide. In the presence of excess tertiary amine the latter was converted into quaternary tetra(hydrocarbyl)ammonium iodide.     

Ruthenium-catalyzed direct amination of alcohols with tertiary amines

A highly selective phosphine-based ruthenium catalyst system efficiently catalyzes the direct amination of alcohols with aliphatic tertiary amines, yielding unsymmetric tertiary amines in yields up to 87%. Ligand and solvent both affect the reaction yields significantly. The reaction can be performed with a wide variety of functionalities.     

Reaction of tertiary cyanoacetylenic alcohols with hydrogen bromide

Conclusions The addition of HBr to tertiary cyanoacetylenic alcohols is accompanied by intramolecular cyclization, which leads to the hydrobromides of bromiminodihydrofurans.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1646–1647, July, 1983.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Oxidative cleavage of silicon-carbon bond with trimethylamine-N-oxide. New access to primary alcohols and aldehydes from terminal alkenes and alkynes

Oxidative cleavage of carbon-silicon bond of organosilanes with trimethylamine-N-oxide is achieved under mild conditions. The reaction occurs chemoselectively irrespective of the presence of amino and thio groups to give formally anti-Markovnikov hydration products of l-alkenes and l-alkynes via hydrosilylation.     

Singlet oxygen promoted carbon-heteroatom bond cleavage in dibenzyl sulfides and tertiary dibenzylamines. Structural effects and the role of exciplexes

The C-heteroatom cleavage reactions of substituted dibenzyl sulfides and substituted dibenzylcyclohexylamines promoted by singlet oxygen in MeCN have been investigated. In both systems, the cleavage reactions (leading to benzaldehyde and substituted benzaldehyde) were slightly favored by electron-withdrawing substituents with rho values of +0.47 (sulfides) and +0.27 (amines). With dibenzyl sulfides, sulfones were also obtained whereas sulfoxide formation became negligible when the reactions were carried out in the presence of a base. Through a careful product study for the oxidation of dibenzyl sulfide, in the presence and in the absence of Ph2SO, it was established that sulfone and cleavage product (benzaldehyde) do not come by the same route (involving the persulfoxide and the hydroperoxysulfonium ylide) as required by the generally accepted mechanism (Scheme 1) for C-heteroatom cleavage reactions of sulfides promoted by singlet oxygen. On this basis and in light of the similar structural effects noted above it is suggested that dibenzyl sulfides and dibenzylamines form benzaldehydes by a very similar mechanism. The reaction with singlet oxygen leads to an exciplex that can undergo an intracomplex hydrogen atom transfer to produce a radical pair. With sulfides, collapse of the radical pair leads to an alpha-hydroperoxy sulfide than can give benzaldehyde by an intramolecular path as described in Scheme 3. With amines, the radical pair undergoes an electron-transfer reaction to form an iminium cation that hydrolyzes to benzaldehyde. From a kinetic study it has been established that the fraction of exciplex converted to aldehyde is ca. 20% with sulfides and ca. 7% with amines.     

F-Induced decomposition of 3-[(3-tert-butyldimethylsiloxy)phennoxy]-3-phenyl-1,2-dioxetanes without C---C bond cleavage of the dioxetane ring

F⁻-induced decomposition of 3-[3-(tert-butyldimethylsiloxy)phenoxy]-3-phenyl-1,2-dioxetane (5c) yielded an intramolecular redox product (7b), whereas 3-phenoxy-3-(3-siloxyphenyl)-1,2-dioxetane (3) gave normal carbonyl fragments with intense light emission. An isomer (5a) gave light with normal decomposition by CIEEL, though the major process was one to yield an acyloin (7a).     

Chemo- and regioselective modification of l-histidine with tertiary cyanopropargylic alcohols

l-Histidine chemo- and regioselectively reacts with tertiary cyanopropargylic alcohols (4,4-di-alkyl-4-hydroxybut-2-ynenitriles) under mild conditions (water, 6.4 wt.% NaOH, 5—15 °C, 72—175 h) with the formation of new “unnatural” amino acids containing an iminodihydrofuran substituent in the amino group (50—70% yields).     

Amide bond cleavage: acceleration due to a 1,3-diaxial interaction with a carboxylic acid

To independently assess the contribution of ground-state pseudoallylic strain to the enormous rates of amide bond cleavage in tertiary amide derivatives of Kemp's triacid, we have studied four amide derivatives of (1alpha-3alpha-5beta)-5-tert-butyl-1,3-cyclohexanedicarboxylic acid. Our results demonstrate that absent pseudoallylic strain, a 1,3-diaxial interaction of an amide with a carboxylic acid leads to only a 2400-fold increase in the rate of amide bond cleavage as compared with the rate of hydrolysis of an unactivated peptide bond.     

The nature of the active states during photochemical reactions of anthraquinone dyes with alcohols

It was established that addition of anthracene or naphthalene reduced the luminescence intensity of anthraquinone dyes, observed during their photoreaction with alcohols (fluorescence of their hydrogenated products). It was shown that this effect was linked with excitation energy migration from the dyes to the additives at the triplet levels. It was concluded that during photohydrogenation the triplet state of weak as well as strong anthraquinone sensitizers was active.