Exchange route to oxyphosphoranes

Denney, B Donald; Chang, Bennie C.; Conrad, Walter E.; Denney, Dorothy Z.; Edelman, Robert; Powell, Rachael; White, Dennis W.

doi:10.1021/ja00745a031

Cited by 15 publications

(3 citation statements)

References 6 publications

(10 reference statements)

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“…Mitsunobu reactions with diols have been shown to proceed through a 5-membered 1,3λ-dioxaphospholane intermediate [112–114], which then extrudes phosphine oxide resulting in the epoxide. With P( n- Bu) 3 , a highly reactive phosphine such as phosphorane has been observed only twice before when the simple substrate ethylene glycol was used as the diol [115–116]. Operating under cryogenic conditions, we were able to observe the phosphonium betaine as well as the dioxaphospholane intermediate and confirmed its 1,2- cis stereochemistry by NMR.…”

Section: Reviewsupporting

confidence: 52%

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

Downey

Hocek

2017

Beilstein J. Org. Chem.

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Glycosylation is an immensely important biological process and one that is highly controlled and very efficient in nature. However, in a chemical laboratory the process is much more challenging and usually requires the extensive use of protecting groups to squelch reactivity at undesired reactive moieties. Nonetheless, by taking advantage of the differential reactivity of the anomeric center, a selective activation at this position is possible. As a result, protecting group-free strategies to effect glycosylations are available thanks to the tremendous efforts of many research groups. In this review, we showcase the methods available for the selective activation of the anomeric center on the glycosyl donor and the mechanisms by which the glycosylation reactions take place to illustrate the power these techniques.

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Section: Reviewsupporting

confidence: 52%

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

Downey

Hocek

2017

Beilstein J. Org. Chem.

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“…In our case we were not able to remove stoichiometric amounts of OP(OEt) 3 (which is more hydrophilic than OP(OiPr) 3 ) through an aqueous work up (without saponification). Moreover, pentavalent P(OEt) 5 prepared from P(OEt) 3 with diethylperoxide and ethylbenzenesulfonate, respectively, in an additional step, was reported to effect cyclodehydration of diols to furans and pyrans [47–48] (for recent examples for cyclodehydration protocols see [49–50]). Thereby, the volatile products were separated from O=P(OEt) 3 through distillation.…”

Section: Introductionmentioning

confidence: 99%

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

Huy

Westphal

Koskinen

2014

Beilstein J. Org. Chem.

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SummaryA concise (5 to 6 steps), stereodivergent, highly diastereoselective (dr up to >19:1 for both stereoisomers) and scalable synthesis (up to 14 g) of cis- and trans-2-substituted 3-piperidinols, a core motif in numerous bioactive compounds, is presented. This sequence allowed an efficient synthesis of the NK-1 inhibitor L-733,060 in 8 steps. Additionally, a cyclodehydration-realizing simple triethylphosphite as a substitute for triphenylphosphine is developed. Here the stoichiometric oxidized P(V)-byproduct (triethylphosphate) is easily removed during the work up through saponification overcoming separation difficulties usually associated to triphenylphosphine oxide.

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“…This led to the question of the effect of a six-membered ring in 1,3,2-dioxaphosphorinanes on the stereochemical course and the mechanism of substitution at phosphorus. In this case, the diequatorial or apical-equatorial positions of the ring in the TBPI are equally probable and are not connected with the essential strain energy changes [9].The stereochemistry of the displacement reactions at phosphorus was intensively investigated using the geometrical cisand trans-isomers of the structurally diverse 1,3,2-dioxaphosphorinanes shown in Figure 2. In this place, it is interesting to note that 1,3,2-dioxaphosphorinanes may be considered as oversimplified analogues of cyclic nucleotides-adenosine 3 ,5 -phosphate (c-AMP) and thiophosphate (c-AMPS).…”

Section: Figurementioning

confidence: 99%

Nucleophilic Substitution at Tetracoordinate Phosphorus. Stereochemical Course and Mechanisms of Nucleophilic Displacement Reactions at Phosphorus in Diastereomeric cis- and trans-2-Halogeno-4-methyl-1,3,2-dioxaphosphorinan-2-thiones: Experimental and DFT Studies

et al. 2021

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Geometrical cis- and trans- isomers of 2-chloro-, 2-bromo- and 2-fluoro-4-methyl-1,3,2-dioxaphosphorinan-2-thiones were obtained in a diastereoselective way by (a) sulfurization of corresponding cyclic PIII-halogenides, (b) reaction of cyclic phosphorothioic acids with phosphorus pentachloride and (c) halogen–halogen exchange at PIV-halogenide. Their conformation and configuration at the C4-ring carbon and phosphorus stereocentres were studied by NMR (1H, 31P) methods, X-ray analysis and density functional (DFT) calculations. The stereochemistry of displacement reactions (alkaline hydrolysis, methanolysis, aminolysis) at phosphorus and its mechanism were shown to depend on the nature of halogen. Cyclic cis- and trans-isomers of chlorides and bromides react with nucleophiles (HO−, CH3O−, Me2NH) with inversion of configuration at phosphorus. DFT calculations provided evidence that alkaline hydrolysis of cyclic thiophosphoryl chlorides proceeds according to the SN2-P mechanism with a single transition state according to the potential energy surface (PES) observed. The alkaline hydrolysis reaction of cis- and trans-fluorides afforded the same mixture of the corresponding cyclic thiophosphoric acids with the thermodynamically more stable major product. Similar DFT calculations revealed that substitution at phosphorus in fluorides proceeds stepwise according to the A–E mechanism with formation of a pentacoordinate intermediate since a PES with two transition states was observed.

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Exchange route to oxyphosphoranes

Cited by 15 publications

References 6 publications

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

Nucleophilic Substitution at Tetracoordinate Phosphorus. Stereochemical Course and Mechanisms of Nucleophilic Displacement Reactions at Phosphorus in Diastereomeric cis- and trans-2-Halogeno-4-methyl-1,3,2-dioxaphosphorinan-2-thiones: Experimental and DFT Studies

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