Annulations disrotatory ring closure

The Robinson annulation has three distinct steps the Michael addition of the enol or enolate across the double bond of the a,(3-unsaturated ketone to produce a 1,5-diketone (Michael adduct), followed by an intramolecular aldol reaction, which affords a cyclic (3-hydroxy ketone (keto alcohol), and finally a base-catalyzed dehydration which gives rise to the substituted cyclohexenone. An alternative mechanism via disrotatory electrocyclic ring closure is possible. ... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

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