A Facile Synthesis of 7-Methylenebicyclo-[3.3.1]nonan-3-one and its Transformation Leading to the Novel Tricyclic System, Protoadamantane

Transannular Cyclization with Grignard Reagents: Facile Synthetic Routes to Oxaadamantane and Protoadamantane Derivatives

“…17 The formation of protoadamantane derivatives in Grignard reaction of 7 can be explained by keto-enol tautomerisation and subsequent ring-closure reaction with epoxy group forming protoadamantane skeleton, which then reacts again with Grignard reagents (Scheme 2). We found support for this mechanism in the rearrangement of epoxy 8) under the conditions where the enol form of the carbonyl group is favored (KOt-Bu-t-BuOH system) 18 or formation of anion by strong base (sodium or potassium methylsulfinylmethide in DMSO). 19 This is also consistent with the known rearrangement of some bicyclo[3.3.1]nonane derivatives.…”

Synthesis of 1,2-Disubstituted Adamantane Derivatives by Construction of the Adamantane Framework

“…The second effective approach to 1,2-disubstituted adamantane compounds utilizes the cyclization of bicyclic precursors, namely derivatives of bicyclo [3.3.1]nonanes, which can be obtained from simple building blocks (as shown previously) or through the ring opening of readily available 1,3-disubstituted adamantane derivatives [54,55].…”

“…Transmetalation of the Grignard reagent to CeCl 3 gave oxaadamantane derivatives (oxygen atom embedded in the adamantane framework). The cyclization of starting material 168 was first demonstrated using potassium tert-butoxide as a base [54]. The prepared racemic diol 171a was rearranged with perchloric acid in hot aqueous dioxane to afford the racemic 1,3,4-trisubstituted adamantane diol 173 in 80% [92].…”