168333-60-6Relevant articles and documents
Electrophilic reactivity of bisketenes: an experimental and theoretical study, and photoinduced hydration
Allen, Annette D.,Ma, Jihai,McAllister, Michael A.,Tidwell, Thomas T.,Zhao, Da-chuan
, p. 847 - 852 (2007/10/02)
The kinetics of the acid-catalysed hydration of the bisketene 2 (1) are indicative of rate limiting protonation at Cβ followed by hydration to form the (monoketenyl)acetic acid 5, previously proposed as an unobserved intermediate in the neutral hydrolysis of 1.On further reaction 5 undergoes a slower uncatalysed conversion to form the stereoisomeric 2,3-bis(trimethylsilyl)succinic anhydrides 4.Confirmation of the intermediacy of 5 is obtained by its formation and observation on photohydration of 1.Reaction of 1 with one equivalent CF3CO2H yields the ( monoketenyl)acetic trifluoroacetic anhydride 8.Ab initio MO calculations at the MP2/6-31G*//MP2/6-31G* level for proton addition and at the HF/6-31G*//HF/6-31G* level for chloronium ion addition to the parent bisketene buta-1,3-diene-1,4-dione (9) indicate that the most stable products result from attacks at Cα, the carbonyl carbon, while the ions from attack at Cβ are at least 4.7 and 18.4 kcal mol-1 less stable, respectively.Further calculations at the MP2/3-21G//HF/3-21G level indicate that silylation of the bisketene causes a relative favouring of electrophilic attack at Cβ, in agreement with the experimental results.
