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Conversion of Dibenzoxaphosphinines into 2‐Hydroxybiphenyl‐2′‐ylphosphane Ligands and Their BH 3 Adducts: The O–H δ+ ···H δ– –B Hydrogen–Hydrogen Bond
Author(s) -
Wawrzyniak Piotr,
Kindermann Markus K.,
Heinicke Joachim W.,
Jones Peter G.
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201001242
Subject(s) - chemistry , borane , adduct , reactivity (psychology) , hydrogen bond , medicinal chemistry , acylation , hydrolysis , metathesis , hydrogen , boranes , stereochemistry , organic chemistry , catalysis , molecule , polymerization , medicine , polymer , alternative medicine , pathology , boron
Chlorodibenz[ c , e ][1,2]oxaphosphinine 1 Cl reacted with bulky organolithium compounds R 1 Li (R 1 = t Bu, mesityl) under mild conditions to yield organodibenz[ c , e ][1,2]oxaphosphinines 1 R 1 , which underwent ring‐opening metathesis with less bulky organolithium compounds R 2 Li. After O ‐trimethylsilylation, 2‐(trimethylsilyloxy)biphenylylphosphanes 2 were isolated. Reaction of 1 Cl with R 2 Li followed by silylation provided symmetrically P ‐substituted compounds 2 . The formation of compounds 3 and 4 demonstrated the facile hydrolysis and oxidation of 1 R 1 , the formation of compound 5c ox indicated the sensitivity of 2 to hydrolysis and air oxidation. Methanolysis of 2 provided the free hydroxybiphenylylphosphanes 5 (for further modification by O ‐acylation), which were converted into air‐stable borane adducts 6 . The latter were unable to undergo O ‐acylation. Acylation of 5 followed by borane protection afforded O ‐acyloxybiphenylylphosphane–borane adducts, as demonstrated by the formation of compounds 7a and 8a . X‐ray crystal structure analysesrevealed intermolecular O–H ··· H–B hydrogen–hydrogen bonds; for compound 6b the average H ··· H distance is 1.90 Å, whereas for 6e a three‐centre O–H ··· H 2 B interaction (av. H ··· H 2.25 Å) was observed, which is still shorter than twice the van der Waals radius for hydrogen (2.4 Å). To the best of our knowledge this is the first report on hydrogen–hydrogen bonds in functionally substituted phosphane–boranes and may explain the low reactivity at the OH group. Only on stronger heating was hydrogen evolved.