Synthesis and Complexing Properties of [2.n](2,6)Pyridinocrownophanes

Abstract

[2.n](2,6)Pyridinocrownophanes (3a-e) were efficiently prepared by intramolecular [2 + 2] photocycloaddition of vinylpyridine derivatives under irradiation using a 400-W high-pressure mercury lamp through a Pyrex filter. They were of cis-configuration with respect to the cyclobutane ring, which was proven by the specific methine proton NMR resonances at delta 3.98-4.08. From ESI-MS analysis 3a-e were found to form 1:1 complexes with Ag+ cation. In a liquid-liquid extraction, 3 showed the highest affinity toward Ag+ cation among several heavy metal nitrates. In this series, 3c possessing four ethereal oxygen atoms was found to show the highest Ag+ affinity, according to the liquid-liquid extraction and determination of stability constant with the cation. The photoreactivity of precursor vinylpyridines is discussed by the predictor gamma(r(c)) proposed by Caldwell.

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

“… This compound and a related pyridinocrownophane showed a particularly high affinity to silver ions. Various other crown ethers were assembled by the Nishimura group employing related methods. − …”

Ring closing metathesis employing organometallic substrates and the templated synthesis of macrocycles

“…In fact, preparation of both corresponding templates, analogues of complex 19 shown in Scheme 5, for the RCM reaction was complicated by retention of a large portion (gravimetrically determined to be ∼10%) of the by-product Ag salts, formed during the pyridine complexation reaction. The silvercontaining complexes were inactive in RCM, potentially due to metathesis catalyst deactivation, competitive coordination of the olefin with Ag, [76][77][78][79] or to effective shortening of the chain by the formation of poly(ether)-Ag complexes [80,81]. Regardless, this necessitated removal of the remaining Ag salts by reaction with H 2 S to precipitate the remaining silver as AgS.…”

Robust and Scalable Approach to 1,3‐Disubstituted Pyridylcyclobutanes

“…The known approaches to the synthesis of pyridylcyclobutane derivatives include metal‐catalyzed sp 2 ‐sp 3 cross‐couplings of halopyridines, reactions of metallated pyridines, the Minisci or the Barton radical reactions, transformations of pyridine N ‐oxides or their derivatives, as well as other methods . However, most literature examples relied on the [2 + 2] cycloadditions, including photodimerization, intra‐ and intermolecular reactions. Most of these methods were applied for the synthesis of derivatives lacking functional groups at the cyclobutane ring.…”