1 (209)

Esta é uma pré-visualização de arquivo. Entre para ver o arquivo original

206 Organic Chemistry Solutions Manual Finally, the enamine is hydrolysed by reprotonation to the same iminium ion and then water. These steps are the exact opposite of what happens in enamine formation. 0 0 0 0 + + N N N Ho NH H 0 0 0 0 Problem 6 How would you produce specific enol equivalents at the points marked with the arrows necessarily starting from the simple carbonyl compound shown)? 0 0 Purpose of the problem First steps in making enol(ate)s with regiochemical control. Suggested solution Ketones 2 and 3 have two different α positions so there is a good chance that we can control formation directly from the ketone. Ketone 1 is different and enolate formation can be only by conjugate addition. The second enolate is thermodynamic and the third kinetic - methods are shown. 0 Me₂CuLi Me₃SiCI Me 0 OLI 0 Me₃SiCI LDA Et3N THF Problem 7 How would the reagents you have suggested in Problem 6 react with: (a) Br₂; (b) a primary alkyl halide RCH₂Br? Purpose of the problem Moving on from enol(ate) formation to reactions. Suggested solution Two are silyl enol ethers and will react well with bromine to put a bromine atom in the position. The third is a lithium enolate and will certainly react though probably rather Preliminary conversion to a silyl enol ether would solve that problem. 0 OLi 0 0 Br Br₂ Br₂ 1. Br 2. Br₂