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Catalyst‐Free and Catalysed Addition of P(O)–H Bonds to Allenyl/Alkynyl‐Phosphonates and ‐Phosphane Oxides: Use of a Robust, Recoverable Dinuclear Palladium(I) Catalyst
Author(s) -
Srinivas Venu,
Balaraman E.,
Sajna K. V.,
Kumara Swamy K. C.
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.201100197
Subject(s) - chemistry , geminal , catalysis , palladium , reactivity (psychology) , medicinal chemistry , organic chemistry , medicine , alternative medicine , pathology
Abstract An effective, recoverable, dinuclear palladium(I) catalyst [(OCH 2 CMe 2 CH 2 O)PSPd(PPh 3 )] 2 has been explored and compared with other traditional palladium catalysts (e.g., [Pd(PPh 3 ) 4 ]) in the phosphonylation/phosphanylation ofallenes (OCH 2 CMe 2 CH 2 O)P(O)CH=C=CH 2 ( 1 ), Ph 2 P(O)CH=C=CH 2 ( 2 ), (EtO) 2 P(O)CH=C=CH 2 ( 3 ) (OCH 2 CMe 2 CH 2 O)P(O)CH=C=CMe 2 ( 4 ), Ph 2 P(O)CH=C=CMe 2 ( 5 ), (OCH 2 CMe 2 CH 2 O)P(O)C(Ph)=C=CH 2 ( 6 ) and Ph 2 P(O)C(Ph)=C=CH 2 ( 7 ). The phosphonylation/phosphanylation, in general, occurred at the carbon β to the phosphorus atom, but the concomitant proton addition took place at the α or γ positions leading to either allyl‐ or vinyl‐phosphonates. The use of P( n Bu) 3 as catalyst led to geminal and bis‐phosphonylation/phosphanylation with less substituted =CH 2 terminal allenes 1 and 2 . In conjunction with the use of the corresponding isomeric alkynes 8 and 9 , as many as five different types of phosphonylated products have been synthesized. The reactions with the more substituted allenes 4 – 7 gave single products in most cases. Several examples of catalyst‐free, solvent‐free phosphanylation reactions are also described. The reactivity of the phosphonylating/phosphanylating agents was found to be (OCH 2 CMe 2 CH 2 O)P(O)H ( 10 ) < (OCH 2 CMe 2 CH 2 O)P(S)H ( 11 ) < Ph 2 P(O)H ( 12 ) ≈ Ph 2 P(S)H ( 13 ). The catalytic activity of the recoverable dinuclear palladium(I) complex [(OCH 2 CMe 2 CH 2 O)PSPd(PPh 3 )] 2 ( 14 ), which poses interesting questions about the mechanistic pathway, is briefly highlighted. Structures of the dinuclear palladium(I) catalyst 14 and the key products were determined by X‐ray crystallography.