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Topic: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane  (Read 2922 times)

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Offline Karina280594

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Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
« 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??

Offline AWK

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Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
« Reply #1 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.
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Offline Karina280594

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Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
« Reply #2 on: December 02, 2016, 02:19:10 AM »
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?

Offline AWK

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Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
« Reply #3 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.
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Offline Karina280594

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Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
« Reply #4 on: December 02, 2016, 08:26:57 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! :-)

Offline orgopete

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Re: Mechanism for making 2,2-dimethyl-4-phenyl-1,3-dioxolane
« Reply #5 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.
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