Show how you would use Robinson annulations to synthesize the following compounds. Work backward, remembering that the cyclohexenone is the new ring and that the double bond of the cyclohexenone is formed by the aldol with dehydration. Take apart the double bond, then see what structures the Michael donor and acceptor must have.
Here we have to show the synthesis of the following compounds by Robinson annulations
The Robinson Annulation reaction involves the formation of six-membered rings in polycyclic compounds, such as steroids. It combines two reactions: the Michael Addition and the Aldol Condensation reaction.
Synthesis of 2-methyldicyclohex-2-enone
The 1st step involves generation of nucleophile, which will added with ketone (1-ethylprop-2-en) and forms 3-cyclohexanone-1-ethylpropane, which in presence of a base release one molecule of H2O and forms carbanion ion (intermediate), which undergoes rearrangement reaction involves breaking of C=O and formation of C-C followed by base catalysed reaction and forms 2-methyl-3-hydroxydicyclohexanone which on heating release one molecule of water and forms
2-methyldicyclohex-2-enone as the product.
(cyclohexanone) ( 3-cyclohexanone-1-ethylpropane)
( 3-cyclohexanone-1-ethylpropane) (Intermediate)
(2-methyl-3-hydroxydicyclohexanone) ( 2-methyldicyclohex-2-enone)