Dioxaphospholane 2-oxide

Hydrophosphorylation has recently been extended to rhodium catalysts as a route to anti-Markovnikoff products.198 Thus, 3mol.% Rh(PPh3)3Cl affords the ( )-alkenylphosphonates (R = H, Ph, -Cr,I I ]3, CH2CH2CN, SiMe3, or cyclohexenyl) in high yields (>80%) at room temperature when 4,4,5,5-tetramethyl-l,3,2-dioxaphospholane-2-oxide (74) is used as the PH source (Equation (19)).199 The rate of reaction is highly solvent dependent... 

Alkenes are much less reactive in the H-P bond addition reactions than alkynes. However, 1,3,2-dioxaphospholane 2-oxide (4a), a five-membered hydrogen phosphonate of pinacol, is exceptionally reactive with alkenes although dialkyl and diaryl phosphonates such as 4b-d are totally unreactive (Scheme 25) [26]. Very interestingly, six-membered hydrogen phosphonates 4e,f are also unreactive under identical conditions. 

R1 = R2 = CH3 2-(2-Chlor-1-methyl-elhylj-4,5-dimethyl-l,3,2-dioxaphospholan-2-oxid 80%... 

Phenyl-tetrafluor-phosphoran reagiert mit Hexamethyl-l,3,2-dioxasilolan in To uol bei 110° (76 Stdn.) zum 2-Phenyl-tetramethyl-/,3,2-dioxaphospholan-2-oxid (50% Schmp. 108-110°)462 ... 

Alkoxy(Aryloxy)-l,3,2-dioxaphospholan-2-oxide reagieren mit Natriumcyanid in Di-methylsulfoxid oder Dimethylformamid bei 60—80° zu Phosphorsaure-monoalkyl(aryl)-estem (60-95%)36 37 ... 

Amino-l,3,2-dioxaphospholan-2-oxide werden mitguten Ausbeuten durch mehrstiin-diges Erwarmen mit Natriumcyanid in Dimethylsulfoxid zu Phosphorsaure-monoamiden (55-95%) gespalten50 ... 

Alkoxy-l,3,2-dioxaphospholan-2-oxide werden durch Natriumcyanid/Dimethylform-amid zu Natriumsalzen von Phosphorsaure-alkylester-(2-cyan-ethylestern) (84—90%) ge spalten108 ... 

Wahrend die Einwirkung von Dimethylamin auf 2-Phenoxy-l,3,2-dioxaphospholan-2-oxid Phosphorsaure-(2-dimethyIamino-ethylester)-phenylester liefert (s.S. 505), erhalt man aus den 4-Methyl- bzw. 4,5-Dimethyl-Analogen die entsprechenden Phosphorsau-re-dimethylamid-(2-hydroxy-alkylester)-phenylester(> ... 

Dimethyl-2-hydroxy-1,3,2-dioxaphospholan-2-sulfid-Iiiiidazoliuni-Salz 5 Zu ciner L6sung von 2,72 g (0,02 mol) 4,5-Dimethyl-1,3,2-dioxaphospholan-2-oxid und 1,36 g (0,02 mol) Imidazol in Benzol gibt man 0,64 g (0,02 mol) Schwefel. Nach 2 Stdn. wird das auskristallisierte Salz abgesaugt und aus Propanol/Ethylether umkristallisiert. Ausbeute 2g(85%) Schmp. 117-118°. 

Dimethyl-2-hydroxy- -sulfid-Imidazolium-Salz aus 4,5-Dimethyl-1,3,2-dioxaphospholan-2-oxid und Imidazol E2, 663... 

The chlorination, or bromination, of 2-(2-chloro-l,2-alkadiene)-l,3,2-dioxaphospholane 2-oxide results in ring enlargement to 2-halogenoethyl-2-oxo-5,6-dihydro-... 

The interaction of 2-cyanomethyl-4,5-dimethyl-l,3,2-dioxaphospholan 2-oxide and hexamethyldisilazane produces a complex system of products which involves ring-chain tautomerism and migrations of silyl groups from N to O. In the solid phase the product has the structure (126) but, in solution, the pentaco-ordinate structure (125) predominates, although, depending on the actual solvent, structures (127) or (128) are discernible by means of i.r. spectroscopy. ... 

A mixture of the allylphosphonate 156 and alkenylphosphonates 157 and 158 was obtained by the Pd-catalyzed hydrophosphorylation of 1,2-heptadiene with 4,4,5,5-tetramethyl-l,3,2-dioxaphospholane-2-oxide (155) using Pd(PPh3)4 as a catalyst. When PdMe2(dppf) was used, the allylphosphonate 156 was obtained regioselectively in 87% yield [51]. The allylphosphonium salts such as 159 were... 

Figure 3 Phosphorus-containing chiral derivatizing agents. [4] 2-chloro-3,4- dimethyl- 5-phenyl -1,3,2-oxazophospholidine-2-sulfide [5] 2-chloro-4,5-dimethyl-1,3,2-dioxaphospholane-2-oxide [6] 2-dimethyl amino-1,3-dimethyloctahydro-1 H-1,3,2-benzodiazaphosphole [7] 5,5-dimethyl-2-hydroxy-4-phenyl-1,3, 2-dioxaphosphonan-2-oxide [8] L-menthyl(phenyl)phosphoryl-chloride [9] 2-chloro-1,3-dimenthyl-4,5-diphenyl-1,3,2-diaza-phosphole [10] dichloro(menthyl)phosphine.

Stereoselective addition of a chiral cyclic phosphite to a cyclic imine was applied to the synthesis of phosphonic analogs of d- and L-penicillamine41. Enantiomerically pure dioxaphospholane oxide 6 underwent addition to 2,5-dihydro-2,2,5,5-tetramethylthiazole in the presence of boron trifluoride as a catalyst. The diastereomeric adducts 7, obtained in a 2 1 ratio, were easily separated on silica gel and their configuration assigned by X-ray analysis the (4/ )-isomer was shown to be the major diastereomer. Hydrolysis of each diastereomer gave pure enantiomers of phosphopenicillamine 841. 

The halogenation of the allenesubstituted 2-oxo-l,3,2-dioxaphospholanes also leads to 2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives 182 (Scheme 72) [99]. 

Reactions.—Nucleophilic Attack at Carbon. (/) Carbonyls. Methyl arylglyoxylates react with trisdimethylaminophosphine (TDAP) to form m-a/S-dimethoxycarbonyl-stilbene oxides.63 The initially formed zwitterion (61) reacts with a second molecule of the ester to form a fra/ -diphenyl-1,4,2-dioxaphospholan intermediate, which undergoes a concerted symmetry-allowed retrograde n2s + 4 cycloaddition to give a carbonyl ylide, conrotatory cyclization of which leads to the cw-oxirans (62) (Scheme 3). 

Unter Ringspaltung sind auch 2-Amino-l,3,2-dioxaphospholan- bzw. -1,3,2-phosphori-nan-2-oxide leicht entalkylierbar z.B.149 ... 

The majority of the publications in the field of oxidative addition of HFA to tertiary phosphanes deal with the formation and properties of l,3,2-A -dioxaphospholanes 57 (60,61). These compounds are generally stable when the a carbon atoms do not bear hydrogen atoms. Heterocycles with a hydrogen atoms are stable up to about 70°C at this temperature the isomeric phosphetanes are formed. The syntheses of some sterically hindered phosphoranes require drastic conditions. 

In addition to the compounds 57, 60, and 61 listed in Tables II-IV, further l,3,2-2 -dioxaphospholanes are accessible via halogen exchange reactions 106,115, 229, 230, 232, 263, 263a, 277) (vide infra), oxidative addition of a,/S-diketones to 2 -dioxaphospholanes (32), hydrolysis of silylamino compounds with HCl to yield unsubstituted amines (121), and thermal elimination of McsSiF from the silylaminofluoro derivatives 57ah and 57ai (115,118). 

A -Dioxaphospholanes show no inversion at the phosphorus atom, which can be seen in the nonequivalence of the CFj groups (273). A -Dioxaphospholanes 73 can be oxidized with halogens to form A -dioxaphospholanes 74 (228). Exchange of the halogens in 73a-c with suitable reaction partners (e.g., LiNHj) yields substituted A -phospholanes [e.g., 73g (265)] (see also Section III,A,2). 

Dioxaphospholan 2-(Bis-[2-chlor-ethyl]-amino)-4-ethoxy-methyl- -2-oxid XII/2, 414f. 

Finally, the stereospecificity of the phosphorane-promoted cyclodehydration is adequately demonstrated in the reaction of d,Z-2,3-butanediol (9) with DTPP in CD2CI2 (35 C, 10 h). The stepwise nature of the cyclodehydration process gives exclusively d5-2,3-epoxybutane (10 >99%) by NMR analysis [6 12.9 (CH3) and 52.4 (CHO)] (76). This latter result is consonant with the previous findings of Denney etal. 24) where a mixture containing 88% d,/- and 12% zne5o-4,5-dimethyl-2,2,2-triethoxy-1,3,2X5-dioxaphospholanes (11) gave a mixture of 85% cis- and 15% /rans-2,3-butene oxides (10), respectively, during tiiermolysis (117°C, 42 h) (equations 2 and 3). Polymeric Dioxaphospholanes. 

Dioxaphospholans.— Triphenylphosphine and the 1,2-dioxetan (26) give a high yield of the phosphorane (27), which decomposes at 55 °C to give phosphine oxide and epoxide. The dihalogenophosphoranes (28) and (29) were obtained as shown. 

The 4,5-dioxo-l,3,2-dioxaphospholane (128) has been prepared and subjected to thermal or MS fragmentation an intense peak corresponding to (129) was found in the El mass spectrum, and thermolysis gave (130), both results in accordance with a facile formation of the arylphosphinidene oxide (129) from (128). Pyrolysis of the cyclic phosphites (131) gave a deposit on a — 195°C cold finger which according to P NMR contained some aryl phosphenite (132), the chemistry of which could be studied for the first time. A full paper has appeared on the preparation and properties of the stable ylidylphosphinidene chalcogenides (133). ... 

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