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Synthesis and conformational studies of chiral macrocyclic [1.1.1]metacyclophanes containing benzofuran rings.

Authors
  • Islam, Md Monarul
  • Tomiyasu, Hirotsugu
  • Matsumoto, Taisuke
  • Tanaka, Junji
  • Rahman, Shofiur
  • Georghiou, Paris E
  • Redshaw, Carl
  • Yamato, Takehiko
Type
Published Article
Journal
Organic & Biomolecular Chemistry
Publisher
The Royal Society of Chemistry
Publication Date
Sep 14, 2015
Volume
13
Issue
34
Pages
9055–9064
Identifiers
DOI: 10.1039/c5ob01002k
PMID: 26220058
Source
Medline
License
Unknown

Abstract

Macrocyclic [1.1.1]metacyclophanes (MCPs) containing benzene and benzofuran rings linked by methylene bridges and which can be viewed as calixarene analogues, have been synthesized by demethylation of [3.3.1]MCP-diones with trimethylsilyl iodide (TMSI) in MeCN. The [3.3.1]MCP-diones are synthesized by using (p-tolylsulfonyl)methyl isocyanide (TosMIC) as the cyclization reagent in N,N-dimethylformamide (DMF) with an excess of sodium hydride. (1)H NMR spectroscopy revealed that the remaining hydroxyl group on the phenyl ring is involved in intramolecular hydrogen bonding with the oxygen of one of the benzofuran rings. O-Methylation at the lower rim of monohydroxy[1.1.1]MCP in the presence of K2CO3 in acetone afforded a novel and inherently chiral calixarene analogue, namely the macrocyclic [1.1.1]MCP, possessing C1 symmetry. The inherent chirality of the two conformers was characterized by (1)H NMR spectroscopy by addition of an excess of Pirkle's chiral shift reagent, which caused a splitting of the corresponding methylene protons to AB patterns. Single crystal X-ray analysis revealed the adoptation of a hemisphere-shaped cone isomer. DFT calculations were carried out to investigate the energy-minimized structures and the hydrogen bonds of the synthesized MCPs.

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