Hello, everyone today we will discuss chemoselectivity and stereoselective reaction questions and answer. Few difficult questions for CSIR NET Gate IIT JAM and other entrance examinations. This is one type of conceptual question in the reaction and reagent section. Discussion of the reaction mechanism of carbon-carbon single bond formation.
This conversion uses the suitable Regents for the formation of the chemoselective intermediate. This intermediate has produced the product in the right pathway. The stereoselectivity of this reaction does not mention Whiteley. The formation of chemoselective intermediate very widely used chemoselective reagent.
Problem-solve:
First of all, read the questions carefully and try to understand your best knowledge from the basic reagent theory class. If your reaction mechanism concept has clear then you can try to solve this question easily.
Q.5. Convert with proper reagents, and mentioned the reaction mechanism:
Answer: Questions no.5
The product formation of active Alpha position hydrogens is forward to more active using the specific reagent. correspond to Alpha position protection for the asymmetric compound.
The technique is to block one of the alpha positions by introducing a removable substituent which prevents the formation of the corresponding enolate.
Use of an asymmetric compound which is the formation of a chemoselective product. Chemoselective means the possibility of two types of product formation using the different reagents.
Note
The reaction that produced the product using a favorable position (less substituent and more substituent position), causes two different types of product forms as possible. The effect of reagents is chemoselectivity. This is a Chemoselective reaction and formation of a chemoselective product.
Reaction mechanism of reagents session questions no.5
The given conversion proper reagents are used and classified the two types:
- Conversion part-1 with the reaction mechanism
- Conversion part-2 with the reaction mechanism
Conversion part-1 (Reaction mechanism):
Preparation of 9-alkyl-1-decalone (as a mixture of cis and trans isomers) Blocking the Alpha position then add The Regent of t-BuOK, t-BuOH. Using this reagent formation of possible enolate then added the methyl iodide in case of alkylation of formation of of of possible intermediate. After this reaction blocking Alpha-position Group deprotects using the Base KOH and ethylene glycol regent. And finally the formation of the required product.
In this conversation, we have to use several types of reagents that are favorable for the protection and deprotection of the Alpha position given compound. The reagents are are
The protection or blocking Alpha position Use those reagents:
- Na-OEt, EtOH, HCO2Et
- BuSH, TsOH
For the alkylation of a given compound and formation of corresponding Corresponding enolate using those reagents:
- t-BuOK, t-BuOH and MeI
For the deprotect Alpha position blocking group we have to use the reagents:
- KOH, H2O, ethylene glycol, reflux
Finally, we have to get the cis and trans racemic mixture product of 9-alkyl-1-decalone.
Conversion part-2 (Reaction mechanism)
On the other hand, the formation for preparation of 9-methyl-1-decalone uses the reagent only t-BuOK, t-BuOH, and MeI. That process is favorable for the active Alpha hydrogen abstract procedure. We have to proceed with the simple alkylation using the more stable and more favorable enolate intermediate formation.
Reference Books and research article:
You can follow problem-solving in Carruthers’s book for modern organic synthesis. The book is an advanced-level book for an entrance exam aspirant. Students follow this book for clearing the concept.