The Mitsunobu Reaction: Origin,Mechanism, Improvements,and Applications

The Mitsunobu reaction is a widely used and versatile method for the dehydrative oxidation–reduction condensation of an acid/pronucleophile usually with a primary or secondary alcohol that requires the combination of a reducing phosphine reagent together with an oxidizing azo reagent. The utility of this reaction stems from the fact that it is generally highly stereoselective and occurs with inversion of the stereochemical configuration of the alcohol starting material. Furthermore, as carboxylic acids, phenols, imides, sulfonamides, and other compounds can be used as the acid/pronucleophile, this reaction is useful for the preparation of a wide variety of functional groups. This Focus Review of the Mitsunobu reaction summarizes its origins, the current understanding of its mechanism, and recent improvements and applications.     

Suzuki-Miyaura coupling reaction of aryl chlorides using di(2,6-dimethylmorpholino)phenylphosphine as ligand

Suzuki-Miyaura coupling was achieved on a variety of aryl chlorides by using di(2,6-dimethylmorpholino)phenylphosphine (L1) as a bulky electron-rich monoaryl phosphine ligand. We report the couplings of various chlorobenzenes and heteroaryl chlorides.     

Anchored palladium bipyridyl complex in nanosized MCM-41: a recyclable and efficient catalyst for the Kumada-Corriu reaction

A palladium bipyridyl complex anchored onto nanosized mesoporous silica MCM-41 catalyzed the cross-coupling of aryl iodides or bromides with Grignard reagents to provide the corresponding biaryls in high yields. The reaction proceeded smoothly with an equal molar amount of substrate and Grignard reagent in the presence of 0.2-0.02 mol % of catalyst in THF at 50 °C or under refluxing conditions. The catalyst prepared may be used in a very low percentage, recovered after reaction, and re-used.     

Reactivation pathway of the hydrogenase H‐cluster: Density functional theory study

This work puts forth a reaction pathway for the reactivation of exogenous ligand inhibited H‐cluster, the active site of Fe‐only hydrogenases. The H‐cluster is a dimetal complex, Fe–Fe, with the metal centers bridged by di(thiomethyl)amine. Exogenous ligands, H₂O, and OH^?, are bound to the distal iron (Fe_d). Density functional theory (DFT) calculations on the native and ruthenium‐modified H‐cluster have been performed using the B3LYP functional with 6‐31+G** and 6‐311+G** basis sets. We have ascertained that there is a thermodynamically favorable pathway for the reactivation of the OH^? inhibited H‐cluster, which proceeds by an initial protonation of the Fe_d–OH^? complex. The proposed reaction pathway has all its intermediate reactions ensue exothermically. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

二氯亚甲基锗烯与乙烯环加成反应机理的理论研究

The mechanism of a cycloaddition reaction between singlet dichloromethylene germylene and ethylene has been investigated with B3LYP/6-31G＊ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD（T）//B3LYP/6-31G＊ method. On the basis of the surface energy profile obtained with CCSD（T）// B3LYP/6-31G＊ method for the cycloaddition reaction between singlet dichloromethylene germylene and ethylene, it can be predicted that the dominant reaction pathway is that an intermediate INT1 is firstly formed between the two reactants through a barrier-free exothermic reaction of 61.7 kJ/mol, and the intermediate INT1 then isomerizes to an active four-membered ring product P2.1 via a transition state TS2, an intermediate INT2 and a transition state TS2.1, in which energy barriers are 57.7 and 42.2 kJ/mol, respectively.     

Ba2Cu3O5+δ as an intermediate phase during the synthesis of YBa2Cu4O8

We propose a reaction model for the synthesis of YBa₂Cu₄O₈ under normal pressure conditions, which contains 4 partial reaction steps. In a first step bariumnitrate and copperoxide react to Ba₂Cu₃O_5+δ. This substance will be formed for each mixtures Ba:Cu=2∶3...3∶2. The following two partial reaction steps are connected to Ba₂Cu₃O_5+δ, which reacts with Y₂O₃ and CuO to YBa₂Cu₄O₈ or decomposes to BaCuO₂ and CuO. In a last step parts of BaCuO₂ reacts with Y₂O₃ and CuO to YBa₂Cu₄O₈.     

Direct synthesis of hetero-biaryl compounds containing an unprotected NH2 group via Suzuki-Miyaura reaction

Hetero-biaryl compounds were prepared via the Suzuki-Miyaura coupling reaction of hetero-aryl moieties containing an unprotected NH₂ group and arylboronic acids. D-t-BPF was found to be an efficient ligand for the cross-coupling of NH₂-unprotected hetero-aryl chlorides with phenylboronic acid.     

Heck reactions of aryl bromides with alk-1-en-3-ol derivatives catalysed by a tetraphosphine/palladium complex

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ efficiently catalyses the Heck reaction of alk-1-en-3-ol with a variety of aryl bromides. In the presence of hex-1-en-3-ol or oct-1-en-3-ol, the β-arylated carbonyl compounds were selectively obtained. Linalool and 2-methylbut-3-en-2-ol led to the corresponding 1-arylalk-1-en-3-ol derivatives. Turnover numbers up to 69,000 can be obtained for this reaction. A minor electronic effect of the substituents of the aryl bromide was observed. Similar reaction rates were observed in the presence of activated aryl bromides such as bromoacetophenone and deactivated aryl bromides such as bromoanisole.     

Use of epoxidation and epoxide opening reactions for the synthesis of highly functionalized 1-oxaspiro[4.5]decan-2-ones and related compounds

Epoxidation of ethyl 3-(6-hydroxycyclohex-1-en-1-yl)propanoate (11) provided the syn epoxide 12. By invoking chelation controlled epoxide opening the triol derivatives 13 and 14 or the spiro lactone 25 could be obtained. Elimination of HBr from the bromides 26 and 27 produced the spiro cyclohexenones 28 and 29. Epoxidation of the double bond occurred in a diastereoselective manner to give epoxides 30 and 31, respectively. Treatment of the epoxide 31 with LiBr/AcOH gave the bromo hydrin 38. In a ‘merry go round’ fashion 38 was further functionalized on the cyclohexane ring by elimination, epoxidation, and epoxide opening resulting in the bromo hydrin 43. Other cyclohexane derivatives that were produced during these studies include the cyclohexenone 19 and the cyclohexanediol 23. In addition, enolate azidation of the spiro lactone 29 proceeded in a diastereoselective manner providing the α-azido lactone 32.     

The Efficient Synthesis of the Optically Active β‐Hydroxyl‐γ‐Butyrolactone Derivatives

The optically active β‐hydroxyl‐γ‐butyrolactones were synthesized from nonchiral starting material by employing reductive cleavage reaction, sharpless asymmetric epoxidation and dihydroxylation, and Lewis acid‐catalysed cyclization as key steps. This strategy can be used to prepare many chiral β‐hydroxyl‐γ‐butyrolactone analogues.