3404-61-3Relevant articles and documents
Light-driven biocatalytic reduction of α,β-unsaturated compounds by ene reductases employing transition metal complexes as photosensitizers
Peers, Martyn K.,Toogood, Helen S.,Heyes, Derren J.,Mansell, David,Coe, Benjamin J.,Scrutton, Nigel S.
, p. 169 - 177 (2015/12/31)
Efficient and cost effective nicotinamide cofactor regeneration is essential for industrial-scale bio-hydrogenations employing flavin-containing biocatalysts such as the Old Yellow Enzymes. A direct flavin regeneration system using visible light to initiate a photoredox cycle and drive biocatalysis is described, and shown to be effective in driving biocatalytic activated alkene reduction. Using Ru(ii) or Ir(iii) complexes as photosensitizers, coupled with an electron transfer mediator (methyl viologen) and sacrificial electron donor (triethanolamine) drives catalytic turnover of two Old Yellow Enzymes with multiple oxidative substrates. Therefore, there is great potential in the development of light-driven biocatalytic systems, providing an alternative to the reliance on enzyme-based cofactor regeneration systems.
Polylithiumorganic compounds. Part 28. The reaction of allene and alkyl substituted allenes with lithium metal
Maercker, Adalbert,Tatai, Andrea,Grebe, Burkhard,Girreser, Ulrich
, p. 1 - 8 (2007/10/03)
The reaction of allene (3a) and alkyl substituted allenes 1,2-hexadiene (3b), cyclopropylallene (3c), and vinylidene cyclopropane (3d) with lithium metal was investigated in order to access 2,3-dilithioalkenes 4a-d. These dilithioalkenes 4a-d are very reactive in polar solvents like THF and act as strong bases, either metalation of the starting allene 3a-d, the solvent, or sufficiently acidic intermediates like 8 a-d is observed. The metalation products 5-7 show follow-up reactions like 1,3-H shift to the corresponding 1-lithio-1-alkynes 8 and subsequent metalation to the dilithioalkynes 9. Additionally, lithium hydride elimination and ring-chain rearrangement (for 5c) are observed. 1,2-Hexadiene (3b) can be brought to reaction with lithium metal in the apolar solvent pentane, here the follow-up reactions are much slower due to the insolubility of 4b. In all cases the elucidation of the reaction pathways is hampered by the formation of complex mixtures of, amongst others, regio- and stereoisomeric products upon quenching with simple electrophiles.
METAL-HALOGEN INTERCHANGE BETWEEN t-BUTYLLITHIUM AND 1-IODO-5-HEXENES PROVIDES NO EVIDENCE FOR SINGLE-ELECTRON TRANSFER
Bailey, William F.,Patricia, Jeffrey J.,Nurmi, Timo T.,Wang, Wei
, p. 1861 - 1864 (2007/10/02)
No products attributable to cyclization of 5-hexen-1-yl radicals have been detected in reactions of t-butyllithium with 1-iodo-5-hexenes at -78 gradC.Such experiments provide no evidence for the intermediacy of free-radicals in the metal-halogen interchange of primary alkyliodides with t-C4H9Li.
Reactions of Methyl-Substituted Hex-5-enyl and Pent-4-enyl Radicals
Beckwith, Athelstan L. J.,Easton, Christopher J.,Lawrence, Tony,Serelis, Algirdas K.
, p. 545 - 556 (2007/10/02)
Relative and absolute kinetic data have been determined for ring closure of methyl-substituted hex-5-enyl radicals: 2-methyl-(10a), 3-methyl-(4a), 4-methyl-(5a), 2,2-dimethyl-(10c), 3,3-dimethyl-(4c) and 4,4-dimethyl-hex-5-enyl (5c) radicals, generated by interaction of tributylstannane with the corresponding bromides (1a)-(3a) and (1c)-(3c).Each radical undergoes regiospecific or highly regioselective 1,5-cyclization more rapidly than does the unsubstituted radical (4d).The rate enhancements, which arise mainly from lowering of the activation energy, can be rationalized in terms of the gem-dimethyl effect. 1,5-Ring closures of monosubstituted species are stereoselective: 2-methyl- and 4-methyl-hex-5-enyl radicals (10a) and (5a) give mainly trans products, whereas 3-methylhex-4-enyl radical gives mainly the cis.This behaviour reflects the effect of the substituent on the stabilities of cyclic transition complexes in chair-like conformations.Ring closure of 2,2-dimethylpent-4-enyl radical or of 3,3-dimethylpent-4-enyl radical (19) could not be detected.
CYCLIZATION OF C7-ALKANES OVER Pt BLACK CATALYST
Zimmer, H.,Paal, Z.,Tetenyi, P.
, p. 513 - 532 (2007/10/02)
C6-and C5-cyclization of heptane isomers (and also, olefin formation as a related process) over Pt-black have been studied in pulse and circulation systems.Hydrogendeficient conditions favour aromatization, via presumably terminal olefins.C5-Cyclization in the presence of more hydrogen is accompanied by internal olefin formation.Relative reactivities of all heptane isomers have been measured; this shows that cyclization is easier between terminal methyl groups.Optimum hydrogen pressures for both types of cyclization have been determined (and compared with hydrogenolysis, too).Earlier mechanism suggestion for aromatization and cyclopentane formation have been confirmed; the distinction between two types of bond shift mechanisms producing aromatics (from substituted pentanes) and saturated isomers, respectively, has recieved additional support facilitating the identification of these two reactions with mechanisms proposed in the literature.
