Reaktion #814319

Reaktionsgleichung

phosphonium bromide

phenylmethyltriphenylphosphonium bromide

n-butyllithium

1,4-cyclohexanedione mono-ethylene ketal

→

8-phenylmethylene-1,4-dioxaspiro[4.5]-decane

Reaktionsbedingungen

Vorschrift

For example, when n is the bridging group --CH2 --, an appropriately substituted or unsubstituted phenylmethyl bromide, for example, 2-chlorophenylmethyl bromide, is reacted with triphenylphosphine in toluene, affording the corresponding phenylmethyltriphenylphosphonium bromide. The so-prepared phosphonium bromide is then treated with n-butyllithium, and reacted with 1,4-cyclohexanedione mono-ethylene ketal, yielding the appropriate 8-phenylmethylene-1,4-dioxaspiro[4.5]-decane. The 8-phenylmethylene-1,4-dioxaspiro[4.5]-decane is in turn reduced with hydrogen gas in the presence of 10% palladium on charcoal, giving the corresponding 8-phenylmethyl-1,4-dioxaspiro[4.5]-decane. The 1,4-dioxaspiro functional group is then cleaved from the so-prepared molecule with acetic acid and water, affording the corresponding 4-phenylmethylcyclohexanone. The 4-phenylmethylcyclohexanone is then reacted with cyanoguanidine, as previously described, yielding the targeted 2,4-diamino-6-phenylmethyl-5,6,7,8-tetrahydroquinazoline. Example 2 provides a detailed description of how this reaction is conducted.

Quelle