The formal (4+1) cyclization between in situ generated achiral carbonyl-stabilized ammonium ylides and vinylogous p-quinone methides can be carried out under operationally simple conditions, leading to two different double bond regioisomers depending on the conditions used. Apart from these racemic approaches, a first proof-of-concept for enantioselective versions of these reactions was also obtained.
Key words
ammonium ylides - quinone methides - cyclization - regioisomers - stereoselectivity