Syntheses of diaza[1.1.1] and [1.1.1.1] paracyclophanes by smiles rearrangement

Abstract

Highly strained diaza[1.1.1] and [1.1.1.1]paracyclophanes were synthesized using Smiles rearrangement (paracyclophane is hereafter abbreviated as PCP). Smiles rearrangement allowed the synthesis of compounds with bridging groups, which could not be obtained using the previously reported Chapman rearrangement method. The two synthetic methods are complementary to each other and therefore useful for the synthesis of diaza[1n]PCP. However, in Chapman rearrangement, the diaza[1.1.1]PCP precursor is a rigid molecule and the precursor could not be synthesized. In contrast, the Smiles rearrangement uses a PCP-precursor rearrangement with low distortion; thus, [1.1.1]PCP can be obtained. Furthermore, the syntheses of 1a and 2 can be performed on a gram scale. However, due to their low solubility, the molecular structure could not be confirmed by crystallographic analysis; therefore, these structures were optimized by DFT calculations and discussed.