Michael addition five-membered carbocycles

Carbocyclization of m-alkcnyl-z-methoxybcnzy I lithiums to form five- or six-membered rings has been studied 101 the five-membered ring is formed with a cis-stereochemical relationship between the methoxy substituent and the adjacent methyl group. Intramolecular carbolithiation of vinyl sulfides at — 105°C in THF has been found to occur non-stereospecifically with regard to the newly formed C—Li centre.102. The stereochemistry of selective tandem Michael addition alkylation reactions of vinylphosphonates has been explored.103... 

Hassner and coworkers have developed a one-pot tandem consecutive 1,4-addition intramolecular cycloaddition strategy for the construction of five- and six-membered heterocycles and carbocycles. Because nitroalkenes are good Michael acceptors for carbon, sulfur, oxygen, and nitrogen nucleophiles (see Section 4.1 on the Michael reaction), subsequent intramolecular silyl nitronate cycloaddition (ISOC) or intramolecular nitrile oxide cycloaddition (INOC) provides one-pot synthesis of fused isoxazolines (Scheme 8.26). The ISOC route is generally better than INOC route regarding stereoselectivity and generality. 

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