Methyl ketones ethylene derivs., synthesis

This sequence transforms acyclic ketones and aldehydes into a-methylene ketones and a-methyl-a,)5-unsaturated ketones and aldehydes It has been illustrated by the synthesis of eucarvone, ( )-nuciferal and ( )-manicone This ring-opening of chlorosiloxycyc-lopropanes with ClSiMea elimination appears to be a practical route to Z or a,)5-ethylenic aldehydes and ketones depending on the stereochemistry of the reactants. For example, conversion in MeOH-NEta at 20°C of the 2-chloro-2-methyl-3-pentyl-l-trimethylsiloxycyclopropanes (derived from the addition of the chloromethylcarbene to the E and Z silyl enol ethers of n-heptanal) leads either to or Z 2-methyl-oct-2-enal (equation 65). ... 

In a paper published along with that of Stevens and Wentland20 and in agreement with these authors, Keely and Tahk23 reported the independent synthesis of dl-mesembrine, also from I-methyl-3-(3,4-dimethoxyphenyl)-2-pyrroline and methyl vinyl ketone. In their work the cyclopropyl derivative 3b was prepared from the reaction of the anion of 3,4-dimethoxyphenylacetonitrile (lc) with ethylene dibromide in dimethyl sulfoxide and its sodium salt as solvent and base. Reduction with ethereal diisobutylaluminum hydride gave the aldehyde, which was condensed with excess methylamine in benzene-ether solution with calcium oxide as the dehydrating agent. 

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