Linear free energy relationships in the Bergman cyclization of 4-substituted-1,2-diethynylbenzenes
摘要:
A series of 4-substituted- 1,2-diethylnylbenzenes were prepared (1a-f) and subjected to Bergman cyclization. Bulk cyclization proceeded to produce the corresponding 2-substituted naphthalenes (2a-f) in good yields (59-78%). Kinetic experiments show a linear free energy relationship between the cyclization rate and the Hammett sigma(m) substituent coefficient and the Swain-Lupton field and resonance parameters. (C) 2000 Elsevier Science Ltd. All rights reserved.
AFM-Induced Amine Deprotection: Triggering Localized Bond Cleavage by Application of Tip/Substrate Voltage Bias for the Surface Self-Assembly of Nanosized Dendritic Objects
摘要:
An alpha,alpha-dimethyl-3,5-dimethoxybenzyloxycarbonyl (DDZ)-protected amine monolayer can be selectively deprotected by the application of a voltage bias from a conducting AFM tip to afford localized nanoscale patterns that can be visualized by self-assembly of dendritic molecular objects with terminal carboxylic acid groups and different aspect ratios.