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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Karina280594 on December 01, 2016, 03:22:30 PM

Title: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
Post by: Karina280594 on December 01, 2016, 03:22:30 PM
Hey,

Could someone help me with the mechanism of this reaction:

Styreneoxide reacting with acetone to give 2,2-dimethyl-4-phenyl-1,3-dioxolane and Cu(OTf)2 is an Lewis acid in the reaction??
Title: Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
Post by: AWK on December 01, 2016, 04:44:30 PM
TReaction of formation of acetonides with epoxides is well known. Search literature and show us your attempt.
Title: Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
Post by: Karina280594 on December 02, 2016, 02:19:10 AM
Quote from: AWK on December 01, 2016, 04:44:30 PM
TReaction of formation of acetonides with epoxides is well known. Search literature and show us your attempt.

So my attempt would be like shown on the picture. I'm a bit confused about how the epoxide would act. Do the epoxide open before the acetone attack?
Title: Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
Post by: AWK on December 02, 2016, 03:22:42 AM
Quote
Do the epoxide open before the acetone attack?

I only know that in presence TiCl3OTf as catalyst this reaction is higly stereospecific, and almost non-stereospecific with anhydrous CuSO4.
In the case of racemic oxirane it does not matter.
Title: Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
Post by: Karina280594 on December 02, 2016, 08:26:57 AM
Quote from: AWK on December 02, 2016, 03:22:42 AM
Quote
Do the epoxide open before the acetone attack?

I only know that in presence TiCl3OTf as catalyst this reaction is higly stereospecific, and almost non-stereospecific with anhydrous CuSO4.
In the case of racemic oxirane it does not matter.

Allright! Thanks! :-)
Title: Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
Post by: orgopete on March 14, 2017, 11:16:16 PM
I don't mean to buump this old mechanism, but for what it might be worth, I doubt formation of an alkoxide intermediate. It seems more likely to me that a ROCu-(OTf)2 copper would eliminate a triflate rather than an alkoxide. Such a mechanism would require a somewhat more lengthy mechanism, but I feel would be more likely.