2, 4, 6‐Triarylphosphinines versus 2, 4, 6‐Triarylpyridines: An Investigation of the Differences in Reactivity between Structurally Related Aromatic Phosphorus and Nitrogen Heterocycles. Issue 43 (2nd October 2013)

• Record Type: Journal Article
• Authors: Weemers, Jarno J. M.; Wiecko, Jelena; Pidko, Evgeny A.; Weber, Manuela; Lutz, Martin; Müller, Christian
• Is Part Of: Chemistry. Volume 19:Issue 43(2013)
• Page Start: 14458
• Page End: 14469
• Publication Date: 2013-10-02
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201302441
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The novel atropisomeric pyridine derivative <italic>rac</italic>‐<bold>10</bold> has been synthesized and structurally characterized. In contrast to its phosphorus analogue <bold>3</bold>, axially chiral <bold>10</bold> has a considerably lower rotational barrier as estimated by DFT calculations. However, the presence of the two enantiomers could be confirmed by means of chiral analytical HPLC analysis and by protonation experiments with a chiral acid. Compound <italic>rac</italic>‐<bold>10</bold> could be further dehydrogenated by treatment with DDQ to the benzo(<italic>h</italic>)quinoline derivative <italic>rac</italic>‐<bold>12</bold>. This conversion failed for the phosphorus analogue <italic>rac</italic>‐<bold>3</bold>. Interestingly, although 2, 4, 6‐triarylphosphinines undergo facile CH activation with [Cp*IrCl<sub>2</sub>]<sub>2</sub> in the presence of NaOAc, this reaction does not proceed with the corresponding pyridine derivatives. On the other hand, the latter ones can be selectively <italic>ortho</italic>‐metalated with Pd(OAc)<sub>2</sub>, leading to acetate‐bridged dimeric species, which could be unambiguously confirmed by means of X‐ray crystal structure analysis. The treatment of phosphinines with Pd(OAc)<sub>2</sub> led instead to the formation of the unusual cofacial oxidative coupling products <bold>16</bold> and <bold>17</bold>, which consist of a phosphorus‐containing cage structure.</p> </abstract>