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Modyfikowane i alternatywne reagenty reakcji Mitsunobu

Kołodziejczyk A.S.

Wiadomości Chemiczne

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2010

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[Z] 64, 11-12

1073-1097

EN

The Mitsunobu reaction provides an extremely useful and versatile synthetic route for a large array of products involving formation of a new C-O, C-N, C-S, C-X, or C-C bond. The reaction is a dehydrative coupling of an alcohol with an acid/pronucleophile using a combination of an oxidizing azo reagent and a reducing phosphine reagent -equation (1). The reaction is very popular due to its stereoselectivity and compatibility with a wide range of functional groups. However, the use of this method is complicated by the resulting complex reaction mixtures containing a product, triphenylphosphine oxide and the reduced azodicarboxylate, as well as unreacted starting material. Due to omnipresence of the Mitsunobu reaction, it was a subject of numerous reviews [1-12]. The mechanism and the stereochemical result of the reaction are still thoroughly studied [22-38] and the current, generally accepted mechanism is outlined in Scheme 1. This article provides an overview of the separation-friendly strategies introduced to facilitate product isolation in the Mitsunobu reaction and its modified and alternative mediators. As two comprehensive reviews devoted to modified Mitsunobu reagents and separation techniques facilitating isolation of the condensation product appeared fairly recently [7, 8], this work concentrates on examples of isolation-friendly strategies and studies subsequent to mentioned reviews. Separation facilitating strategies are based on tagging one of Mitsunobu reagents or substrates with a "separation tag" (phase tag, affinity tag), which controls the behaviour of the component and allows to separate the tagged reaction component from untagged ones. There are four main separation techniques used in the Mitsunobu reaction: polymerassisted phase-switching or solid phase immobilization (2.1.1.), acidic/basic aqueous work-up (2.1.2.), fluorous approach (2.1.3.), and post-reaction sequestration. Both phosphine and azodicarboxylate can be attached to insoluble polymer and the derived side-products (phosphine oxide or hydrazodicarboxylate) can be removed by filtration at the end of the reaction. Fluorous tagging makes possible the separation of a fluorous compound from nonfluorous ones either by partitioning between a fluorous and an organic liquid or by fluorous solid-phase extraction (FSPE) - Scheme 6. A fluorous-tagged acid was also applied to achieve inversion of an alcohol configuration (Scheme 8). Another separation-facilitating strategy uses polymerizable Mitsunobu reagents and post-reaction sequestration, e.g. by ring opening metathesis polymerization (ROMP), either of a condensation product (Scheme 9), or side products (impurity anihilation). The scope of the Mitsunobu reaction was greatly widened by introduction of alternative Mitsunobu reagents by the Tsunoda-Itô group [69-79]. Some of these reagents (1-4, Scheme 12) mediate C-alkylation reactions of very weak acids (pK_a > 23) [77, 78]. Several other modified Mitsunobu reagents are also described.

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63Cu and 31P Nuclear Magnetic Resonance for Characterization of Cu(I) Complexes with P-Donor Ligands

Szymańska I.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 7

1095-1117

EN

The analysis of the 63Cu and 31PNMR resonances and the spin-spin coupling patterns for elucidation of the Cu(I) phosphines complexes geometry and ligands' coordination modes in solutions are reviewed. The influences of the steric and electronic properties of P-donor ligands and the dynamic processes in solution on the 63Cu and 31P NMR spectra of Cu(I) complexes are discussed.

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C-Phosphorylated Azoles

Pinchuk A., Yurchenko A. A., Oshovsky G. V., Zarudnitskii E. V., Pushechnikov A. O., Tolmachev A. A.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 8

1137-1146

EN

A method of phosphorylation of heterocycles incorporating 1,3-azole moiety with phosphorus( III) halides is elaborated. As a result, previously unknown azolyldihalogenphosphines are prepared. Influence of heteroatom and quantity of nitrogen atoms in a cycle on the activity of azoles is studied. Reaction of 5-aminopyrazole derivatives with phosphorus(III) halides affords novel phosphorus-containing bi- and tricyclic fused systems