Intensive NMR study of 1‐<i>t</i>‐butyl‐3‐methyl‐2,4‐bis(2,4,6‐tri‐<i>t</i>‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl

Yoshifuji, Masaaki; Osborn, Stefan T.; Arduengo, Anthony J.; Belmore, Kenneth A.; Ito, Shigekazu

doi:10.1002/hc.20684

Cited by 5 publications

(2 citation statements)

References 12 publications

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“…Chemical shifts of the PEt and PMe groups are similar to symmetric 4c (see Experimental Section) and 4d , respectively, and a similar 2 J PP constant for 4a to 4b is observed. As investigated by the intensive nuclear magnetic resonance (NMR) studies on 4b , the cyclic P 2 C 2 biradical shows unique spin–spin coupling properties. In the 1 H NMR spectrum of 4a , no noticeable 2 J PH constant is observed in the PMe moiety, which is comparable to the 2 J PH constant of 0 Hz in the PCH 2 R moiety of symmetric 4c (R = CH 3 ) and 4d (R = H).…”

Section: Resultsmentioning

confidence: 99%

“…Compounds 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h show considerable stability even in air. This process is unique for obtaining unsymmetrically substituted P‐heterocyclic biradicals that show unusual physicochemical properties . Besides the formation of 4 , regioselective protonation and one‐electron oxidation of 3 are reported to afford the corresponding 1,3‐diphosphacyclobutene and 1,3‐diphosphacyclobuten‐4‐yl, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic and stability studies on unsymmetrical 1,3‐dialkyl‐1,3‐diphosphacyclobutane‐2,4‐diyls

Ito

Kikuchi

Miura

et al. 2011

J of Physical Organic Chem

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Air-tolerant 2,4-bis(2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl singlet biradicals can be prepared by utilizing the unique reactivity of a kinetically stabilized PC triple bond compound. In this procedure, we studied the spectroscopic properties of a fundamental unsymmetrical P-heterocyclic biradical containing both PEt and PMe moieties, and the effects of the PCH 2 OMe group in relation to the stability of the P-heterocyclic biradical skeleton. The experimentally observed nuclear magnetic resonance and photo-absorption parameters of 1-ethyl-3-methyl-2,4-bis(2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl were discussed based on our previous findings and density functional theory calculations, suggesting particular structural characteristics of the P-heterocyclic biradical skeleton and aromatic substituent effects on the sp 2 -C atoms in the 4-membered ring. Introduction of the methoxymethyl group in the P 2 C 2 biradical moiety gave more stabilized 1,3-diphosphacyclobutane-2,4-diyl derivatives. In comparison with considerably unstable biradicals bearing propargyl substituents, relatively higher lowest unoccupied molecular orbital energies suggest reluctant oxidation of the P-heterocyclic skeleton.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%