Oxygen Transfer from Carbon to Phosphorus via a Defined ... presence of triethylamine to give a tricyclic phosphorane intermediate 4 which isomerizes to the.
Dibenzoylmethane Reaction with Dichlorophenylphosphine: Oxygen Transfer from Carbon to Phosphorus via a Defined C2P 0 3 Phosphorane Wilhelm V. Dahlhoff*, Kalulu M. T aba [1], and Richard Mynott* M ax-Planck-Institut für Kohlenforschung. Kaiser-W ilhelm-Platz 1, D-4330 Mülheim a.d . Ruhr. FRG Z . Naturforsch. 44b, 41—46 (1989); received August 10, 1988 Tricyclic Phosphorane, Rearrangem ent to Phosphinic Acid Ester, 2D NM R Spectra, 13C NM R Spectra Dichlorophenylphosphine reacts with two equivalents of dibenzoylm ethane at —30 °C in the presence of triethylamine to give a tricyclic phosphorane interm ediate 4 which isomerizes to the m ore stable phosphinic acid ester 5 above 30 °C. The structures of 4 and 5 were determ ined by l3C, 'H shift correlated 2D NMR spectroscopy using long range couplings.
Introduction In the course of our w ork on acetylacetonate che lates [2—5] we have now also investigated the reac tion of dichlorophenylphosphine with some 1,3-diketones. Both dichlorophenylphosphine [6 ] and its ( C O ) 5 C r — [7], (C O ) 5 W - [7] and C p ( C O ) 2 M n - [8 ] derivatives are known to react with acetylacetone to give the dio xaphosphorinane ring system as the main product. This is formed by attack of both P —Cl func tions on a single molecule of acetylacetone, resulting in the removal of an a and a ß proton. Similar reac tions leading to ring formation have also been o b served in the case of dichlorophenylphosphine oxide [9], A s diketones that have no ß protons obviously can n o t react in this m anner, it was decided to eluci date the reaction of dibenzoylm ethane (1,3diphenyl-1,3-propanedione) with dichlorophenyl phosphine. T he results of this study are given below. R esults A solution of dichlorophenylphosphine 2 in T H F was ad d e d dropwise to a solution of dibenzoyl m e th a n e 1 and triethylamine in TH F. A fter removal of the triethylam ine hydrochloride and concentration of the solution at 0 °C a pale yellow solid product 4 was o b ta ined. In its 'P N M R spectrum one major signal ( 8 7 % of the total integral) was observed at —9.6 ppm .
* R eprint requests to Dr. R. M ynott.
W. V. D ahlhoff or Dr.
V erlag der Zeitschrift für N aturforschung, D-7400 Tübingen 0932-0776/89/0100-0041/$ 01.00/0
O n heating 4 above 30 °C, pure 5 was formed, which was isolated in 5 8 % yield after recrystalliza tion. A single resonance was observed in the 'P N M R spectrum of 5 at 25.6 ppm. The quantitative r ea rran g e m en t of 4 to 5 was followed by ''P N M R. Structure Determ ination o f 3 and 4 by NM R Both 4 and 5 contain two groups of atoms derived from dibenzoylm ethane molecules. The signals of the atoms forming the backbon es of these units must be identified and assigned in ord er to determ ine the structures of these products. H ow ever, each com p o u n d contains 9 qu atern ary carbon atoms and 17 different types of C H groups. T he protons of the C H groups in the backbone play a key role in the analysis. T heir 'H N M R signals are easily recognized because these p rotons do not couple with oth e r hydrogen nuclei. T he 1 ’C resonance of the c arbon atom to which each of these protons are bonded was located in a 2 D 1 3 C,*H —chemical shift correlated N M R spectrum [10], The signals of carbon atoms within ca. three bonds of each proton were then iden tified by recording 2 D 1 3 C, 'H-chemical shift correlated N M R spectra optim ized for long range / c . h couplings ( L R -H E T C O S Y ) [10]. A n a lysis o f the N M R spectra o f 4 U nexpectedly, the l?C N M R spectrum of 4 m eas u red at —30 °C has no signals in the carbonyl region. T he signals of the p rotons on C-4 and C - 8 (num bering scheme in Fig. 1), the central methine carbon ato m s of the original diketone units, are a doublet at (3h (H-4) = 6.27 ( 7 p . h = 32 Hz) and a sharp singlet at
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W. V. D ahlhoff et al. ■Dibenzoylm ethane Reaction with D ichlorophenylphosphine
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