Michael additions phospha

Scheme 1.1.13 Solid-base-mediated phospha-Michael additions.

Heteroatom nucleophiles were described less often. Ye and coworkers published a phospha-Michael addition catalysed by prolinol silyl ether catalyst. Another method for constructing a new C-N bond is the aza-Michael addition, that is the addition of nitrogen-based nucleophiles to a,(3-unsaturated aldehydes. Several groups published these type of reactions using diatylprolinol silyl ether as catalyst. " Fustero and coworkers used this reaction as a key step in the synthesis of biologically active chiral heterocycles. Recently, the authors showed the synthesis of quinolizidine alkaloids, such as (-l-)-myrtine, (-)-lupine and (-l-)-epiquinamide. Vicario applied 5-mercaptotetrazoles as nucleophiles towards a range of unsaturated aldehydes. The reaction proceeded via the iminium activation. The... 

An interesting approach to this direction was recently based on an Ireland-Claisen rearrangement triggered by the phospha-Michael addition of silyl... 

A green synthetic protocol under solvent-free conditions for the synthesis of phos-phono malonates (162) from alkenes (160) and phosphorous nucleophiles (161) using nanoflake ZnO at 50°C has been documented (Scheme 9.52) (Hosseini-Sarvari and Etmad 2008). The reaction is an example of one of the most powerful and important C-P bond-forming reactions, which is the phospha-Michael addition. The advantages of this method include mild reaction conditions, a simple set up, high yields, and so on. The formylation of amines (163) with formic add (70) under solvent-free... 

SCHEME 13.60 Knoevenagel condensation/phospha-Michael addition/double cyclization sequence for the synthesis of tetracyclic 2,3,4,lll7-tetrahydro-17/,67f-67, -[l, 2]benzoxaphospholo[2,3-fc][l,2]benzoxa-phosphol-l-ones 254 [98],... 

The Phospha-Michael addition in organic synthesis and biomedical application of fluorinated phosphonates have been the subject of two reviews. ... 

SCHEME 12 Phospha-Michael addition of dibenzo[c.e][l,2]oxaphosphorine oxide (DOPO) to methyl vinyl ketone. 

SCHEME 15 Phospha-Michael additions with 1,2-clihychophosphinine 1-oxides. 

E. Balint, J. Takacs, L. Drahos, G. Keglevich, Microwave-assisted phospha-Michael addition of dialkyl phosphites, a phenyl-H-phosphinate, and diphenylphosphine oxide to maleic derivatives. Heteroatom Chem. 23 (2012) 235-240. 

Enders, D. Saint-Dizier, A. Laimou, M.-I. Lenzen, A. Eur. J. Org. Chem. 2006, 29-49. (Review on the phospha-Michael addition). 

The development of transition metal-free hydroelementation reactions has been a goal for the synthetic community for many years. As mentioned in the previous sections on Michael addition reactions, A-heterocyclic carbenes have been shown to be efficient catalysts for these addition reactions. One of the challenges that must be overcome when using these catalysts is the sensitivity of the catalysts to electrophiles. To circumvent this problem, carbon dioxide adducts have been synthesized and used as precatalysts for the phospha-Michael addition of secondary phosphine oxides to activated alkenes (Scheme 4.45) [96]. The success of this approach hinged on the observation that these adducts underwent cleavage in solution to generate the free carbene and carbon dioxide. The concentration of the free carbene was found to be dependent upon the solvent, and THF was found to be an effective solvent for the... 

SCHEME 4.71 Phospha-Michael additions with retention of chirality [124],... 

SCHEME 4.72 Phospha-Michael additions using carbene catalysts [96],... 

A series of medicinally useful 2- e 2-bisphosphonate substituted ben-zothiazoles (354) and (355) has been synthesised via a copper-promoted domino condensation/S-aiylation/heterotyclisation process (Scheme 104). An efficient and enantioselective phospha-Michael addition of diethyl phosphite to chalcones (356) has been realised in the presence of chiral ytterbium silylamide (358). Thus, targeted y-oxophosphonates (357) have been produced in high yields (84-94%) and with high enantioselectivity (82-94%) (Scheme 105). ... 

In 2012, Keglevich and coworkers reported the catalyst-free synthesis of a series of new >P(0)-substituted maleic derivatives (62) via microwave-assisted phospha-Michael addition of diall l phosphites, ethyl phenyl-H-phosphinate, and diphenylphosphine oxide to Al-phenyl and N-methyl maleimide (61), in most of the cases without any solvent, in good yields (71-98%) and within 3 h (Scheme 29). This method is advantageous over the previously reported method of Jiang et al. in terms of using no solvent or catalyst. 

The first report regarding phospha-Michael additions to enals was made independently and at the same time by the research groups of Melchiorre [71] and... 

Despite the great interest in chiral phosphines and the success in the phospha-Michael addition to enals, only one example of an organocatalytic phospha-Michael reaction to enones can be found in the Uterature. 

Scheme 34.17 Guanidine catalyzed phospha-Michael addition on nitroolefins.

Addition of Phosphorus Nucleophiles to C=C Bonds Phosphorus nucleophiles, both neutral and anionic, undergo addition to activated carbon—carbon double bonds. Such reactions constitute a phosphorus analogous of the conjugate addition, and they are often referred to as phospha-Michael addition. For hydrophosphonylation of inactivated double bonds, radical conditions are a viable option. In the last 15 years, however, an attractive alternative of a transition-metal-catalyzed hydrophosphonylation has also emerged. ... 

Application of a stereoselective phospha-Michael addition to the synthesis of natural product analogs was for the... 

A phospha-Michael addition has also been applied to a stereoselective synthesis of steroid derivatives of type 130 (Scheme 47.32). ° Addition of catalytic amounts of Pd(OAc)2 was not necessary, but it improved the reactivity... 

SCHEME 47.32. Stereoselective, palladium-catalyzed phospha-Michael addition to steroid derivatives. 

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