Claim: While montréalone are unlikely to exist as stable species, substituted montréalone are used as reaction intermediates, a molecular entity which are usually short lived, in the synthesis of other heterocycles.
Evidence: The montréalone parent compound has been studied theoretically, and is unlikely to exist as a stable species. Substituted montréalones with a balance of stability and reactivity have been used as reaction intermediates in the synthesis of other heterocycles. A reaction intermediate or an intermediate is a molecular entity that is formed from the reactants (or preceding intermediates) and reacts further to give the directly observed products of a chemical reaction. Reactive intermediates are usually short lived and are very seldom isolated.