Sims steric

Lee and Hong" described the first direct synthesis of 2-alkyl-5-aryloxazoles 206 from aromatic a-methyl ketones (Scheme 1.57). They used thallium(III)triflate generated in sim to convert a ketone to the a-ketotriflate 204. Reaction of 204 with a nitrile most likely produces a nitrilium salt 205, as proposed by Meyers and Sicar, which subsequently cyclizes to 206. The reaction works well for aliphatic nitriles regardless of steric hindrance. Aromatic nitriles are not as useful,... 

The main factors which are likely to influence the heat of polymerization are (1) steric hindrance in the poljrmer, and (2) hyperconjugation and conjugation effects in monomer and polymer. Sim-flar effects to (1) will be involved in any reaction in which the double bond is opened, and we may therefore compare the AH values with those of hydrogenation and self-polymerization. Except... 

To our knowledge, the only investigation into metal/SAM interactions for OPEs was carried out by Haynie et al. [6]. They studied the interactions between PPB-SH assembled on Au(l 11) and a series of vapor-deposited metals Au, Ti, Fe, Cr, Cu, Ag and Al, via TOF-SIMS. No evidence of any chemical interactions or penetration was found in the case of Au, Fe, Cr, Ag and Al. Tliis was attributed to the high packing density of these monolayers and the consequent steric hindrance toward penetration. In the case of Ti, the vapor-deposition destroyed the molecular array this is important, since, in many molecular electronics experiments, Ti is often us as a "bonding" metal for the formation of molecule-metal connections [2, 23]. In the case of Cu, they found several peaks in the mass spectrum, indicating a potential reaction between the metal and the benzene rings. 

---