Olefins electron-deficient, formal

Two examples of three-components coupling reaction are shown in Reactions (7.77) and (7.78) [27,87]. These radical chain reactions proceeded by the addition of an alkyl or vinyl radical onto carbon monoxide, generating an acyl radical intermediate, which, in turn, can further react with electron-deficient olefins to lead, after reduction, to a formal double alkylation of carbon monoxide. These three-components coupling reactions require the generation of four highly disciplined radical species, which have specific functions during the chain reaction. 

Such J-mctals as Cu(I) [but not Cu(II)], form a variety of compounds with ethenes, for example [Cu(C2H4)(H20)2]C104 (from Cu, Cu2+, and C2H4) or Cu(C2H4)(bipy)+. It is necessary to mention that, of all the metals involved in biological systems, only copper reacts with ethylene [74b]. Such homoleptic alkene complexes can be useful intermediates for the synthesis of other complexes. The olefin complexes of the metals in high formal oxidation states are electron deficient and therefore inert toward electrophilic reagents. By contrast, the olefin complexes of the metals in low formal oxidation states are attacked by electrophiles such as protons at the electron-rich metal-carbon a-bonds [74c]. 

A new synthetic method for the formal addition of alkanes to olefins has been devised. The alkyl mercuric salt (5) reacts with sodium borohydride in the presence of electron-deficient olefins (6) to form the adduct (7). The yield depends on the mode of addition of NaBH4, the temperature, and the salt olefin ratio. 

An organocatalytic asymmetric formal [3 + 2] cycloaddition reaction of isocya-noesters 218 to nitroolefins 210 leading to highly optically active dihydropyrroles 220 was reported by Gong, et al., Scheme 3.70 [87], The proposed mechanism is depicted in Scheme 3.70 the cinchona alkaloid chiral base 219 promote an asymmetric Michael addition of isocyanoesters to electron-deficient olefins (nitroolefins), and subsequent intramolecular cyclization of the intermediate to afford the dihydropyrroles 220. 

The first report of an enantioselective organocatalytic Mukaiyama-Michael reaction involves the use of an amine catalyst during the 1,4-addition of TMSOF to the electron deficient olefin ( )-but-2-enal. The cafalyst is employed as its dinitroben-zoic acid (DNBA) salt (eq 35). Several other substituted TMSOFs are used in this reaction with similar levels of success. A formal enantioselective synthesis of (+)-compactin incorporates this method. ... 

Scheme 4-23. Formal [3+2] cycloaddition of ri -allyl-Fp complexes with electron-deficient olefins.

Reaction of aminocarbene complexes with electron-deficient olefins typically involves a formal Q,p2H-insertion of the carbene carbon atom and affords acyclic products. More electrophiUc pyrrol-derived aminocarbene complexes, however, effect cydopropanation [15]. A recently reported example involves the cydopropa-nation of simple alkenes with aminocarbene complexes (Scheme 11.3) [16]. 

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