Diaminophosphine oxide

A number of P-chirogenic diaminophosphine oxides (DIAPHOXs) 275 derived from aspartic acid were prepared via hydrolysis of triaminophosphine intermediate 274, generated in a fully diastereoselective reaction of triamines 273 with phosphorus trichloride (Scheme 65) [102, 103],... 

The phosphoramidite ligands that are the focus of the remainder of this chapter have prompted the investigation of ligands containing related structures. Iridium complexes of aspartic acid-derived P-chirogenic diaminophosphine oxides (DlAPHOXs) catalyze the amination [62] and alkylation [63] of aUyhc carbonates (Scheme 6). With BSA as base and catalytic amounts of NaPFs as additive, branched amination and alkylation products were obtained from cinnamyl carbonates in excellent yields and enantioselectivities. However, the yields and enantios-electivities were lower for the reactions of alkyl-substituted aUyhc carbonates. Added LiOAc increased the enantioselectivities of aUyhc alkylation products. 

One of the most powerful strategies for asymmetric ring construction is to desymmelrize a preformed ring. Yasamusa Hamada of Chiba University in Japan has reported (J. Am. Chem. Soc. 2004, /26, 3690) that the inexpensive diaminophosphine oxide 2 nicely catalyzes the asymmetric alkylation of the cyclohexanone carboxylate 1 to give 3. Although no examples were given, this asymmetric alkylation would probably work as well with heterocyclic P-ketoesters. 

A ruthenium catalyst derived from a secondary diaminophosphine oxide has been used successfully in the arylation of C-H bonds by aryl tosylates.41... 

The problem of achieving selective monoarylations of 2-arylpyridines was solved by applying a sterically hindered diaminophosphine oxide (72) as preligand [60]. This air-stable preligand allowed the use of tosylates as electrophiles, which are easily... 

Cyclic diaminophosphine oxide 35 ligating to Pd is useful for substitution of allylic carbonates. To access diamines from 2-vinylaziridines the catalyst system constituting 29 meets established standards/ ... 

Nemoto and Hamada [50] has described the development of a new class of chiral phosphorus ligand - aspartic acid-derived P-chirogenic diaminophosphine oxides, DIAPHOXs - and their application to several Pd-catalyzed asymmetric allylic substitution reactions. Pd-catalyzed asymmetric allylic alkylation was initially examined in detail using diaminophosphine oxides 77, resulting in the highly enantioselective construction of quaternary stereocenters. With the use of the Pd-DIAPHOX catalyst system, asymmetric allylic alkylation, asymmetric allylic amination, and enantioselective construction of quaternary carbons were achieved with high ee (up to 97-99% in many cases) (Scheme 24). 

Nemoto T (2008) Transition metal-catalyzed asymmetric reactions using P-chirogenic diaminophosphine oxides DIAPHOXs. Chem Pharm Bull 56 1213-1228... 

Cramer and co-workers reported a Ni-catalyzed asymmetric hydrocarbam-oylation reaction of alkenes with diaminophosphine oxide ligands. The acyl C—H bond of a carbamate group was directly functionalized. It is known that secondary phosphine oxides are usually air-stable and robust preligands because of their unique tautomerization between P and In the presence of bases or transition metals, such an equilibrium can be shifted to the trivalent phosphinous acid and thus provide the opportunity for hetero-bi-metallic catalysis where a late transition metal and an early transition metal can coordinate to the phosphorus atom and the oxygen atom, respectively (Scheme 8.17). 

Bearing this idea in mind, the authors synthesized a class of chiral diaminophosphine oxide ligands and tested them in the Ni-catalyzed intramolecular asymmetric hydrocarbamoylation reactions of formamides 38 with AlMCa as the other metal catalyst (Scheme 8.18). The combination of [Ni(cod)2] and (i ,i )-L3 gave the optimal catalytic activity. Substrates with various substitution patterns were converted smoothly to their corresponding pyrrolidinones 39 in up to 98% yield and 95% ee under very mild conditions. 

A particular type of secondary / -stereogenic diaminophosphine oxide named DIAPHOX (standing for diaminophosphine oxides) was developed by Hamada and co-workers starting from aspartic acid. Scheme 3.11 depicts the preparation of the simplest one. 

Natural L-aspartic acid can be transformed in several steps into triamine 19, which reacts smoothly with phosphorus trichloride to yield diastereomerically pure 20. This triaminophosphine is stable in neutral or mildly acidic aqueous conditions but, interestingly, it suffers a SN2-type hydrolysis upon purification by sihca gel column chromatography with wet ethyl acetate, yielding the desired secondary diaminophosphine oxide in 60% of overall yield from 19. The absolute configuration of the phosphorus atom (i ) could be unequivocally determined by crystallographic analysis. ... 

The new complex (166), generated from the corresponding diaminophosphine oxide and Mc3 Al, has been employed as a chiral ligand for the Ni(0)-catalysed C-H activation of A-homoallyl formamide (163), which provides pyrrolidones (165) via intramolecular hydrocarbamoylation (164) in <94%... 

Donets and Cramer have developed an asymmetric version of these hydrocar-bamoylation reactions using a diaminophosphine oxide ligand (Scheme 5.40, Table 5.11).44... 

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