Mechanism of Gold(I)‐Catalyzed Conia‐ene Reaction of β‐Ketoesters with Alkynes: A DFT Study

Density functional calculations have been performed to comparatively investigate two possible pathways of Au(I)‐catalyzed Conia‐ene reaction of β‐ketoesters with alkynes. Our studies find that, under the assistance of trifluoromethanesulfonate (TfO), the β‐ketoester is the most likely to undergo Model II to isomerize into its enol form, in which TfO plays a proton transfer role through a 6‐membered ring transition state. The coordination of the Au(I) catalyst to the alkynes triple bond can enhance the eletrophilic capability and reaction activity of the alkynes moiety, which triggers the nucleophilic addition of the enol moiety on the alkynes moiety to give a vinyl‐Au intermediate. This cycloisomerizaion step is exothermal by 21.3 kJ/mol with an energy barrier of 56.0 kJ/mol. In the whole catalytic process, the protonation of vinyl‐Au is almost spontaneous, and the formation of enol is a rate‐limiting step. The generation of enol and the activation of Au(I) catalyst on the alkynes are the key reasons why the Conia‐ene reaction can occur in mild condition. These calculations support that Au(I)‐catalyzed Conia‐ene reactions of β‐ketoesters with alkynes go through the pathway 2 proposed by Toste.     

Multinuclear enantiopure titanium self‐assembly complexes—synthesis,characterization and application to organic synthesis

Hexa‐ and nonanuclear titanium complexes were obtained by self‐assembly of titanium(IV)‐tert‐butoxide and D ‐mandelic acid. Suitable single crystals of these complexes were characterized by X‐ray structure analysis. When used with these complexes, aldol adducts were isolated with a high degree of regioselectivity in direct aldol additions of aromatic and aliphatic aldehydes to functionalized unsymmetrical ketones. High syn‐diastereoselectivities were obtained in aldol additions of enolizable aldehydes with hydroxyacetone and methoxyacetone. Copyright © 2007 John Wiley & Sons, Ltd.     

Triple Click Reaction Strategy for Macromolecular Diversity

This Feature Article focuses on the rapidly emerging concept of the “triple click reactions” towards the design and synthesis of macromolecules with well‐defined topology and chemical composition, and also precise molecular weight and narrow molecular weight distribution. The term “triple click reaction” used in this feature article is based on the utilization of three chemically and mechanistically different click reactions for polymer–polymer conjugation and post‐modification of the polymers. Three sequential click reactions of which two are identical should not be considered to be triple click reactions. The triple click reaction strategy for polymer conjugation and post‐modification of polymers is classified in this article based on the resultant architectures: linear and non‐linear structures.     

Complete 1H NMR assignments of pyrrolizidine alkaloids and a new eudesmanoid from Senecio polypodioides

Chemical investigation of the aerial parts of Senecio polypodioides lead to the isolation of the new eudesmanoid 1β‐angeloyloxyeudesm‐7‐ene‐4β,9α‐diol ( 1 ) and the known dirhamnosyl flavonoid lespidin ( 3 ), while from roots, the known 7β‐angeloyloxy‐1‐methylene‐8α‐pyrrolizidine ( 5 ) and sarracine N‐oxide ( 6 ), as well as the new neosarracine N‐oxide ( 8 ), were obtained. The structure of 1 and 8 was elucidated by spectral means. Complete assignments of the ¹H NMR data for 5 , 6 , sarracine ( 7 ), and 8 were made using one‐dimensional and two‐dimensional NMR experiments and by application of the iterative full spin analysis of the PERCH NMR software. Copyright © 2014 John Wiley & Sons, Ltd.     

Orthogonal multiple click reactions in synthetic polymer chemistry

This review highlights the concept of multiple click reaction strategy which is utilized for design and synthesis of well‐defined complex macromolecular structures as well as multifunctionalization of well‐defined polymers. This review examines the click combinations mainly from double to quadruple and additionally from the most frequently used to the least. The present review may also be regarded as an update for recent reviews dealing with specifically double and triple click reaction combinations in synthetic polymer chemistry. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3147–3165     

Radical copolymerization of chlorotrifluoroethylene with 4‐bromo‐3,3,4,4‐tetrafluorobut‐1‐ene

The radical copolymerization of chlorotrifluoroethylene (CTFE) with 3,3,4,4‐tetrafluoro‐4‐bromobut‐1‐ene (BTFB) initiated by tert‐butylperoxypivalate is presented. The microstructures of the obtained copolymers are determined by means of NMR spectroscopies and elemental analysis and show that random copolymers were obtained. A wide range of poly(CTFE‐co‐BTFB) copolymers is synthesized, containing from 17 to 89 mol % of CTFE. In all the cases, CTFE is the less reactive of both comonomers. T_d^10% values, ranging from 163 up to 359 °C, are dependent on the BTFB content. These variations of thermal property are attributed to the increase in the number of C‐H and C‐Br bonds breakdown when the BTFB molar percentage in the copolymer is higher. T_g values range from 19 to 39 °C and a decreasing trend is observed when increasing the amount of BTFB in the copolymer. This observation arises from the higher flexibility of the copolymer when increasing the number of fluorobrominated lateral chains. These original fluoropolymers bearing reactive pendant bromo groups are suitable candidates for various applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1714–1720