1.3- Dipolar cycloaddition of azomethine imines

Stanovnik B, Jelen B, Turk C, Zlicar M, Svete J (1998) 1,3-dipolar cycloadditions of diazoalkanes to pyridazines. Asymmetric 1,3-dipolar cycloaddition of azomethine imines derived from diazoalkane-pyridazine cycloadducts. J Heterocycl Chem 35 1187-1204... 

Copper-catalyzed 1,3-dipolar cycloaddition of azomethine imine 264 with ethyl propiolate 265 with a chiral ferrocenyl bidentate ligand efficiently generated dihydropyrazol[l,2- 7]pyrazolones 266 in very good yields and ee... 

Following the same concept, a three-component stereoselective entry to pyrazolidinones, involving a 1,3-dipolar cycloaddition of azomethine imines and a-oxo-ketenes, was also reported. Thus, the microwave irradiation of a 1 1 1 mixture of a 2-diazo-1,3-diketone, an aldehyde or a ketone, and a substituted hydrazine in toluene led to the expected spiropyrazolidin-3-ones 38 [Scheme 3.301. The success of this reaction demonstrates that a-... 

SCHEME 5.21 1,3-Dipolar cycloaddition of azomethine imines to alkenes and alkynes. 

The 1,3-dipolar cycloaddition of azomethine imines with alkynes could also be well facilitated by an Al203-supported copper hydroxide [Cu(0H) /Al203] (Scheme 4.21). Generally, the desired pyrazolidinones were obtained in good to excellent yields (Yoshimura et al., 2011). 

Dipolar cycloaddition of azomethine imine or nitrile imine-type dipoles with alkenes or alkynes yields nitrogen heterocycles containing two nitrogen atoms in the ring. MeOPEG resin was applied in the solid-phase synthesis of pyrazolines (Scheme 11.13). Resin-bound... 

Although a lot of cycloadditions of nitrone possessing nitrogen and oxygen atoms have been so far developed, the cycloaddition of 1,3-dipoles with two nitrogen atoms is still limited [8b, 13]. We turned our attention to developing the enantioselective 1,3-dipolar cycloaddition of azomethine imines. 

TABLE 11.1 Asymmetric 1,3-Dipolar Cycloaddition of Azomethine Imines 11... 

To synthesize optically active nitrogen-containing chemicals with oxygen functionalities, it would be ideal to employ various types of unsaturated alcohols as a 1,3-dipolarophile. We developed a stoichiometric and a catalytic asymmetric 1,3-dipolar cycloaddition of azomethine imines 11 to a one-carbon homologated homoallylic alcohol 16A as shown in Table 11.5. 

TABLE 11.4 Desymmetrization of l,4-Pentadien-3-ol (13) by the Catalytic Asymmetric 1,3-Dipolar Cycloaddition of Azomethine Imines... 

FIGURE 11.5 Plausible transition state of asymmetric 1,3-dipolar cycloaddition of azomethine imine. 

A DFT study of 1,3-dipolar cycloadditions of azomethine imines with electron-deficient dipolarophiles CH2=CH-CN, CH2=CHC02Me, and dimethyl maleate has successfully predicted the regioselectivity and reactivity and found little evidence of charge transfer in the transition states. ... 

Asymmetric 1,3-dipolar cycloadditions of azomethine imines with terminal alkynes have been catalysed by 11 chiral ligand (8) coordinated metal amides to form N,N-bicyclic pyrazolidinone derivatives. Mechanistic studies have established the factors that determine the regioselectivity of the stepwise reaction. Novel phosphoramidite ligands (9) coordinated with palladium have been used to effect enantioselective synthesis of pyrrolidines by 3-P 2-cycloaddition of trimethylenemethane (from 2-trimethylsilylmethyl allyl acetate) to a wide range of imine acceptors (Scheme 11). ... 

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