Benzo/naphtho-anellated dihydro-1,2-oxaphosphinines and ring-opening to P-tertiary 2-phosphanyl-1,1'-biaryl-2-ol derivatives - Syntheses and Structures

Reaction of naphthylphenol 1a and phenylnaphthol 1b, respectively, with PCl3 in the presence of ZnCl2 gave mixed benzo- and naphtho-anellated 6-chloro-6H-1,2-oxaphosphinines 2a and 2b. Treatment with equimolar amounts of tBuLi led to 6-tBu-substituted mixed-anellated oxaphosphinines 3a and 3b, respectively, and subsequent P-O-ring cleavage with methyllithium and quenching with ClSiMe3 to 2-trimethylsilyloxy-biarylphosphanes 4a and 4b. NMR-Spectra indicated two data sets for 4a but only one for 4b, indicating higher diastereoselectivity in the ring opening of the 1,2-oxaphosphinine 3b with oxygen in 2-position of naphthaline and the bulkier tBuMeP-group at the phenyl ring. Reaction of 4b with o-anisyllithium (2 equiv.) and ClSiMe3 led to the biarylsilylether 5b. Further conversion with (1S)-camphanoyl chloride gave diastereoisomers of the 2'-phosphanylbiaryl camphanate 6b. Structures were proven by characteristic multinuclear NMR data and for 2a and 5d by crystal structure analysis. 5b and 6b might be useful candidates for enantiomer separation and asymmetric transition metal catalysis.

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