Asymmetric Synthesis 2 Flashcards
A Sulfinimines are chiral at sulfur, and are much more stable to hydroloysis than most imines
What is the structure of the following sulfinimie from the following reaction conditions?
How does the structure of a Sulfinimine allow it to operate as a chiral auxilliary?
The dipole translates chiral information
They act like bar magnets where they want to oppose (single bond will not rotate below 120°C)
What is the mechanism for this reaction forming sulfinimines
What product do we form if we react a sufinimine with Grignards
(dichloromethane is a non-coordinating solvent)
Note this is called a Ellman Chiral Amine synethsis
- Chair-like transition state
What is the mechanism for the following reaction, reacting a sulfinimide with Grignards
We produce >90% DE
Once we have formed our specific chiral amine, how do we remove the auxillary?
- React with HCl and Et2O
- Followed by a SN2 reaction
- > 90% ee
What is the product of this reaction
Regenerates the Sulfinimide
(recycling)
This reaction is the catalytic asymmetric synthesis called the Sharpless Epoxidation
This reaction uses the (-) enantiomer of diethyl tartrate - ligand for titanium
And tBuOOH is the stoichiometric oxidant
What is the product
Get a 80-90% yield of a chiral epoxide
>90% ee
How do the different diethyl tartrate isomers attach the reagent resulting in the formation of different chiral epoxides
(-) DET will come from above and deliver the oxygen of the epoxide
(+) DET wil come from below and deliver the opposite epoxide
These chiral expoxide can be useful building blocks
For example, if you react them witth Red-Al
What is the product of this reaction
Results in a regioselective ring-opening
These chiral epoxides can be useful building blocks
For example if you react them with chloroformate and trimethylamine
What is the mechanism and product?
The following molecule (BINAP) here has axial chirality, how?
This molecule is esstentially planar due to the steric clash between the hydrogens upon rotation
How would we characterise this axially chiral compound (Atropisomer)
The bold wedges make an S shape
So is the S isomer
(S) - BINAP
Ruthernium catalysis can direct react reactions towards a specific chiral product
What is the product of the following reaction
Hint - Ru, u for up, hence H binds in the upwards position - as long as DG on RHS
Ruthernium catalysis can direct react reactions towards a specific chiral product
What is the product of the following reaction
98% ee
Ruthernium catalysis can direct react reactions towards a specific chiral product
What is the product of the following reaction
Alkene doesn’t have a DG on the LHS so nothing happens
92% ee
Deydroamino acids are unactivated alkenes, so here we need to use more activated Rhodium catalyst
What is the structure of the specific amino acid formed
