Poly-α-n-alkyl Acrylic Derivatives: Synthesis,Influence of Molecuur Weight and n-Alkyl Group Length on Physical and Physicochemical Properties

Abstract

A series of α-n-alkyl acrylic acid monomers was synthesized and homopolymerized by a radical route. Methylation of polyacids using diazomethane led to the corresponding methyl esters and allowed physicochemical analysis. The thermal stability of polyacids and polymethyl esters is insensitive to the nature of the alkyl group and to the molecular weight. The glass transition temperature, T _g, classically decreases with increases in alkyl group length such as alkyl polymethacrylates. Molecular weight has a drastic influence on T _g for short alkyl groups.     

Dimerization of 1-Isopropenylnaphthalene: Structural Study of the Dimer

1-Isopropenylnaphthalene has been dimerized by cationic initiation. The structure of the dimer does not depend on the initiator. The cyclization of the dimeric ion takes place on carbon 8 (peri). The structure has been established both by x-ray diffractometry and by NMR. The complete crystallographic structure has been determined. The dimers of various substituted isopropenylnaphthalenes have been obtained in the same way and have the same structure.     

Palladium-catalyzed one-pot synthesis of 2-alkyl-2-arylcyanoacetates

A one-pot procedure for the synthesis of 2-alkyl-2-arylcyanoacetates based on a Pd(OAc)2/DPPF (DPPF = 1,1'-diphenylphosphino ferreocene)-catalyzed enolate arylation followed by in situ alkylation has been developed. This procedure tolerates a diverse range of aryl and heteroaryl bromides, and provides a rapid entry to a variety of 2-alkyl-2-arylcyanoacetates in good to excellent yield.     

Evidence of CuI/CuII Redox Process by X‐ray Absorption and EPR Spectroscopy: Direct Synthesis of Dihydrofurans from β‐Ketocarbonyl Derivatives and Olefins

The Cu^I/Cu^II and Cu^I/Cu^III catalytic cycles have been subject to intense debate in the field of copper‐catalyzed oxidative coupling reactions. A mechanistic study on the Cu^I/Cu^II redox process, by X‐ray absorption (XAS) and electron paramagnetic resonance (EPR) spectroscopies, has elucidated the reduction mechanism of Cu^II to Cu^I by 1,3‐diketone and detailed investigation revealed that the halide ion is important for the reduction process. The oxidative nature of the thereby‐formed Cu^I has also been studied by XAS and EPR spectroscopy. This mechanistic information is applicable to the copper‐catalyzed oxidative cyclization of β‐ketocarbonyl derivatives to dihydrofurans. This protocol provides an ideal route to highly substituted dihydrofuran rings from easily available 1,3‐dicarbonyls and olefins.     

Simulation of Temperature Distributions Within Monomer Film During Photopolymerization

Photoinitiated polymerizations are very fast reactions, and consequently significant thermal effects are observed during the reactions. Nevertheless, isothermal conditions are necessary to measure the kinetic constants of polymerization. In the simulation of heat transfer reported in this paper, it is shown that the use of a thin film of monomer at the bottom of a DSC pan, even in the presence of an intermediate polyethylene film, is convenient if the reaction rate is not too high. For example, the temperature increase of the film does not exceed 1°C for a reaction half-time (time to reach 50% conversion) higher than 10 s when the enthalpy of polymerization is chosen as ΔH _R=115 J g^?1.     

A highly enantioselective catalyst for asymmetric hydroformylation of [2.2.1]-bicyclic olefins

Rh(CO)₂(acac)/TangPhos was found to be a highly enantioselective catalyst for asymmetric hydroformylation of norbornylene under mild conditions. Application of the protocol to the desymmetrization of other [2.2.1]-bicyclic olefins gave moderate to excellent enantioselectivity (55-92% ee).     

New catalysts for Suzuki-Miyaura coupling reactions of heteroatom-substituted heteroaryl chlorides

The new air-stable PdCl2[PR2(Ph-R')]2 complexes, readily prepared from commercial reagents, exhibit unique efficiency as catalysts for the Suzuki-Miyaura coupling reactions of a variety of heteroatom-substituted heteroaryl chlorides with a diverse range of aryl/heteroaryl boronic acids. The coupling reactions catalyzed by the new complexes exhibit high product yields (88-99%) and high catalyst turnover numbers (up to 10,000 TON).     

Highly selective rhodium-catalyzed conjugate addition reactions of 4-oxobutenamides

A variety of 4-oxobutenamides 1 were subjected to rhodium-catalyzed conjugate addition with arylboronic acids providing high regio- and enantioselectivity (97:3 to >99:1, >96% ee) and moderate to excellent yields (54-99%). The key to high selectivity is the use of sterically demanding P-chiral diphosphines, such as Tangphos or Duanphos. The product oxobutanamides 2 may be converted to alternate targets by selective derivatization of either the amide or ketone functional group. A stereochemical model predicting the absolute sense of induction was developed based on single-crystal X-ray structures of product and precatalyst.