Copolymerization of 2,2-dimethyltrimethylene carbonate and cyclic esters

The anionic and/or insertion copolymerization of 2,2-dimethyltrimethylene carbonate (DTC) with ϵ-caprolactone (ECL), pivalolactone (PVL) and L-lactide (LLA) is presented with special emphasis on the copolymerization mechanism. Statistical copolymers are obtained by copolymerization of DTC with ECL and with LLA, while with PVL a block copolymer is obtained. The role of transesterification on the microstructure is discussed.     

Regioselective,Asymmetric Formal Hydroamination of Unactivated Internal Alkenes

We report the regioselective and enantioselective formal hydroamination of unsymmetrical internal alkenes catalyzed by a copper catalyst ligated by DTBM‐SEGPHOS. The regioselectivity of the reaction is controlled by the electronic effects of ether, ester, and sulfonamide groups in the homoallylic position. The observed selectivity underscores the influence of inductive effects of remote substituents on the selectivity of catalytic processes occurring at hydrocarbyl groups, and the method provides direct access to various 1,3‐aminoalcohol derivatives with high enantioselectivity.     

Catalytic, Regiospecific End-Functionalization of Alkanes: Rhenium-Catalyzed Borylation under Photochemical Conditions

Approaching a Holy Grail? A regioselective functionalization of alkanes occurs with commercially available rhenium catalysts and borane reagents under photochemical conditions [Eq. (1)]. Mechanistic studies indicate that the regioselectivity results from a direct thermal reaction of a photochemically generated 16-electron boryl complex with alkane.     

The Rotational Spectrum of the p-Fluorotoluene- Argon van der Waals Complex

The microwave rotational spectrum of the p-fluorotoluene-argon van der Waals complex was analyzed with a molecular beam Fourier transform microwave spectrometer. In the frequency splitting of molecular transitions caused by the internal rotation of the methyl group with respect to the aromatic ring is contained the structure and barrier information. Elucidation is reduced by the analysis of internal rotors direction with respect to the principal axis system of the complex the number of possible solutions in the structure. An rs and r0 structure of the complex was calculated from these data. The argon is located 3.541(1) ? above the aromatic ring. By forming the complex, the barrier height of internal rotation is changed. An additional V3 term in the potential function occurs in the complex because the molecular symmetry of the p-fluorotoluene, containing a V6 but no V3 term, is reduced by the argon. For assumed V6 = 144.79(19) GHz or 57.777(76) J/mol, V3 is found to equal 552.0(10) GHz or 220.31(40) J/mol. Copyright 1999 Academic Press.     

A perturbation method applied to the buckling of a compressed elastica

We consider the problem of carrying out an asymptotic analysis for the phenomenon of bifurcation which occurs at critical values of an axial force applied to an elastic column. In the present setting a discontinuous coefficient precludes the possibility of carrying out the usual asymptotic analysis. The problem is overcome via a nonlinear change of independent variables.