Add time:08/31/2019         Source:sciencedirect.com

It may appear that 1,4-dipolar donor, an acceptor with a polarized CC multiple bond and an alkali metal strong base would suffice to execute a successful Hauser-type annulation. However, reasonable understanding of the reaction and the possible competing reactions is warranted for the success. There are examples which prove to be the exceptions of the generalized reaction. For examples, the Tamura annulations with unsaturated ketones are not often successful. It is precluded with simple Michael acceptors such as methyl acrylate and acrylonitrile. There are more than six possible ways by which an expected [4 + 2] anionic annulation may be foiled. This chapter exclusively deals with accessibility of the starting 1,4-dipolar reagents and choice of reaction conditions. In the later part, the factors that influence the successes and setbacks of the anionic annulation chemistry are highlighted.

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