Tetrahydrophosphinine oxide

Reaction of the regioisomers of tetrahydrophosphinine oxide (51) with Na0H-H20-CHCl3 under phase-transfer conditions was found to afford tetrahydrophosphepine oxides (52) through an unexpected path involving isomerization of (51) and cyclopropanation via Michael addition of CCls. (Scheme 21). 

Tetrahydrophosphinine oxide 166 reacts with dichlorocarbene under phase-transfer catalytic conditions giving 7,7-dichloro-1-methyl-3-phenyl-3-phosphabicyclo[4.1.0]heptane (167) in 71% yield. Heating the phosphabi-cyclo[4.1.0]heptane 167 at 220 °C makes the bicyclic ring opening and the simultaneous elimination of hydrogen chloride gives 4-chloro-3-methyl-l-phenyl-2,7-dihydrophosphepin 1-oxide (168), a seven-membered phosphorus heterocycle, in 67% yield (Scheme 54) [66]. 

Tetrahydrophosphinine oxide 131 was reacted with dichlorocarbene generated from CHC13 by addition of sodium hydroxide under phase-transfer conditions to give adduct 140 which underwent thermal expansion to give 2,7-dihydrophosphepin oxide 141 <1998JCM210> (Equation 29). 

Keywords 1,2-Dihydrophosphinine oxide, 1,2,3,4,5,6-Hexahydrophosphinine oxide, P-Oxophosphoranes, 2-Phosphabicyclo[2.2.2]octene derivative, 1,2,3,6-Tetrahydrophosphinine oxide,... 

Ring Expansion of 2,5-Dihydro-lH-Phosphole Oxides to 1,2-Dihydro- and 1,2,3,6-Tetrahydrophosphinine Oxides... 

The conformational situation of the tetrahydrophosphinine oxides 25t was evaluated on the basis of stereospecific VPH NMR coupling constants. In the case of the major regioisomer (25J, an equilibrium mixture of two half-chair forms was substantiated (Fig. 1) [24],... 

Conformation of the 1-alkoxy-tetrahydrophosphinine oxides (25, Y = alkoxy) was the subject of a separate study. Stereospecific couplings suggested that regioisomers 25x and 252 adopt the half-chair2 conformation. It is quite surprising that the dimethyl derivatives (26) exist in the boat1 conformation (Fig. 3) [17]. 

It can be seen that the conformational situation of 1,2,3,6-tetrahydrophosphinine oxides is highly sensitive towards substitution effects. 

The 1,2-dihydrophosphinine oxide (5,) —> 1,2,3,6-tetrahydrophosphinine oxide (41) transformation shown in Scheme 19 was found to be of general applicability. A variety of P-substituted dihydrophosphinine oxides (14) were converted to tet-rahydrophosphinine oxides (42) by the addition of borane to the reactive a,P-double-bond followed by hydrolysis of the boryl intermediate so obtained (Scheme 20) [31]. 

A series of 3-phosphinoxido- and 3-phosphono-l,2,3,6-tetrahydrophosphinine oxides (47) was synthesized by the addition of diphenylphosphine oxide and dialkyl phosphites on the electron-poor a,p-double-bond of 1,2-dihydrophosphinine... 

Conformation of the 3-P(0)Z2-tetrahydrophosphinine oxides (47) was evaluated, in the first approach, by high level quantum chemical calculations, suggesting that these P-heterocycles prefer adopting one of the twist-boat conformations (in the first place transl or perhaps cisl) (Fig. 7) [34],... 

The 3-dimethylphosphono-l-phenyl-tetrahydrophosphinine oxide (49) is a good example to show two P = O - HC interactions of similar type at the same time. Beside the Aj interaction, similar to that shown in Fig. 8, there is a similar interaction between the oxygen of the ring P = O and the suitable CH unit of the exocyclic dimethylphosphono moiety (A2) (Fig. 9) [34],... 

In this context the most interesting model compound was 3-diethylphosphono-1-ethoxy-tetrahydrophosphinine oxide (50), as three different kind of stabilizing... 

The dibenzylphosphono-tetrahydrophosphinine oxide (52) was transformed into the free phosphonic acid (53) by debenzylation that was found to exist in a half-chair conformation stabilized by an intramolecular H-bonding (Scheme 24, Fig. 11) [34],... 

The diphenylphosphinoxido-phenyl-tetrahydrophosphinine-oxide (48) was also investigated by single crystal X-ray analysis. The P-heterocycle contained one molecule of crystalline water that served as an intramolecular pincer. The intramolecular H-bonding between the exocyclic P = O and a suitable hydrogen atom of the C(6)H2 suggested by quantum chemical calculations could also be proved experimentally (Fig. 12) [35],... 

It was found that, on the basis of the configuration of the ring-P atom, the stereostructure corresponds to cisl as shown in Fig. 7. Intermolecular interactions holding the tetrahydrophosphinine oxide units together in the crystal could also be observed in the packing diagram. 

A novel bidentate P-ligand was prepared from the 3-diphenylphosphinoxido-l-phenyl-tetrahydrophosphinine oxide (54, Z = Ph) by double deoxygenation. Reaction of the bisphosphine (64) so obtained with dichlorodibenzonitrileplatinum (II) afforded cis chelate complex 65 (Scheme 29) [39],... 

A 3-phospholene oxide, a 1,2,3,6-tetrahydrophosphinine oxide and a 2,3,4,7-tetrahydrophosphepine oxide were prepared by a novel molybdenum-catalyzed asymmetric ring closing metathesis (Scheme 2). ... 

The S3mthesis of another kind of bidentate P-ligand was based on the addition of >P(0)H species at the end of the a,p-double bond of 1,2-dihydrophosphinine oxides (42). As the double bond was not too reactive, the activation of the >P(0)H reagent by MesAl was necessary prior to the addition to obtain the 3-phosphono- ((R0)2P(0)-), 3-phosphinoyl- (Ph2P(0)-), and other related ((EtO)PhP(0)-)l,2,3,6-tetrahydrophosphinine oxides (43) (Scheme 15) [61,62]. Under MW irradiation, there was no reaction. The 3-substituted-l,2,3,6-tetrahydrophosphinine oxides (43) were converted to the fully saturated 1,2,3,4,5,6-hexahydrophosphinine oxides (44) by catalytic hydrogenation (Scheme 15) [63,64]. 

The 3-phosphinoyl-l-phenyl-l,2,3,6-tetrahydrophosphinine oxide (45) and the 3-phosphinoyl-l-phenyl-1,2,3,4,5,6-hexahydrophosphinine oxide (48) were converted to the corresponding c/s-chelate Pt complexes 47 and 50, respectively, after double deoxygenation followed by complexation by dichlorodibenzonitrile platinum (Scheme 16) [65,66]. 

V. Ujj, A. Kerenyi, A. Laki, E. Fogassy, G. Keglevich, Optically active 6-membered P-heterocycles 1-phenyl-1,2-dihyclrophosphinine oxide and l-phenyl-3-diphenylphosphinoyl-l,2,3,6-tetrahydrophosphinine oxide, Lett. Org. Chem. 7 (2010) 110-113. 

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