Nitroacetate skeleton

Chemoselective C-alkylation of the highly acidic and enolic triacetic acid lactone 104 (pAl, = 4.94) and tetronic acid (pA, = 3.76) is possible by use of DBU[68]. No 0-alkylation takes place. The same compound 105 is obtained by the regioslective allylation of copper-protected methyl 3,5-dioxohexano-ate[69]. It is known that base-catalyzed alkylation of nitro compounds affords 0-alkylation products, and the smooth Pd-catalyzed C-allylation of nitroalkanes[38.39], nitroacetate[70], and phenylstilfonylnitromethane[71] is possible. Chemoselective C-allylation of nitroethane (106) or the nitroacetate 107 has been applied to the synthesis of the skeleton of the ergoline alkaloid 108[70]. 

Kurth and co-workers utihzed two 13DC reactions in the same sequence for the synthesis of bis-isoxazolo substituted piperidinone skeleton 214 (Scheme 51) [ 154]. The reaction sequence involved Michael addition of an unsaturated alkoxide 207 to j6-nitrostyrene 75a followed by INOC or ISOC. The resulting isoxazoline intermediate 209 was subjected to Grignard addition for the generation of the isoxazolidine moiety 211, which upon DCC-mediated coupling with nitroacetic ester 212 furnished the intermediate 213 bearing both nitroalkane and alkene moiety. This intermediate upon INOC reaction led to the bis-isoxazolo piperidinone nucleus 214. 

E. Enantioselective Palladium-catalyzed Carbocyclization of a Nitroacetate for the Eigoline Skeleton... 

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