Michael ring closure sequential

A one-pot sequential Michael-Michael ring closure (MIMIRC) reaction using 2-cyclo-hexenone as the initial Michael acceptor allowed an effective construction of various polyfunctionalized polycyclic compounds (Scheme 50)210. 

SEQUENTIAL MICHAEL-MICHAEL-RING CLOSURE REACTIONS FOR 3-DIFFERENT-COMPONENT. ONE-POT, 2+2+2 CONSTRUCTION OF ACYLCYCLOHEXENES AND AN ACYLCYCLOHEXANOL. 

More recently, the synthesis of 3-norcephalosporin 72 has been performed successfully by reaction of either allenoate 70 or 3,4-disubstituted 2-butenoates 73a and 73b with copper(i) chloride and tributyltin hydride in NMP <1996GG2705, 1999J(P1 )3463>. Conversion of the allenoate 70 into 72 took place through Michael addition of copper(l) hydride to the central carbon of the allene moiety of 70 and subsequent ring closure of adduct 71. The sequential reaction could be performed successfully by treatment of 70 with copper) 0 chloride and tributyltin hydride in NMP at room temperature, affording 72 in 79% yield without any detectable amount of the A2-isomer (Scheme 16). 

The products obtained from the reaction of (chloromethyl)trimethylsilane with organolithium reagents depend very much on the structure of the lithium compound. While lithium 2,2,6,6-tetramethylpiperidide initiates an a-elimination as described above, the treatment with sec-butyllithium leads to the formation of chloro(trimethylsilyl)methyllithium (11). This reagent cyclopropanates an electron-deficient alkene through sequential Michael addition and intramolecular ring closure (MIRC reaction), for example, the formation of cyclopropane 12. 

Silicon-substituted cyclopropanes can also be generated by the reaction of electron-deficient alkenes with silyl-substituted carbanions bearing a leaving group. This transformation proceeds via sequential Michael addition and intramolecular ring closure (MIRC reaction). 

Examples of the use of [ C]Meldrum s acid are shown in Figure 6.125. In the first case, isopropyl 3-amino[2- C]crotonate 14201. formed upon treatment of the /3-ketoester underwent ring closure by sequential Michael addition to the a-methoxycarbonyl... 

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