I would like some help with these questions. Thank you! A variation on the Fisch
ID: 994712 • Letter: I
Question
I would like some help with these questions. Thank you!
A variation on the Fischer indole synthesis allows the formation of the 4-azaindole as shown below. The intermediate hydrazone undergoes a [3, 3] sigmatropic shift to form the product indole [55]. Write a mechanism for the reaction and identify the [3,3] shift. An enzymatic Diels-Alder reaction has been reported in the biosynthesis of solanapyrones [58]. When this reaction was carried out in the lab, the endo product predominated in all cases, more so as solvent polarity increased. Propose an explanation based on the orbitals involved.Explanation / Answer
since transition state of DA reaction is more polar than starting meterial so polar solvent is stabilised the trasition state. Now in endo product there is an other factor called extened overlap in this case c=o group of lactone's pi electron participate in extented conjugation which make the transition state even more polar than exo trantion state so with increasing polarity of solvent endo increase. More over extented conjugation makes the endo product major in all case.