Se-based Alkene Formation

Question 1

How do analogous selenyl chlorides (ArSeCl) compare to sulfenyl chlorides (ArSCl)?

Answer 1

Selenyl chlorides proceed at lower temperatures (-78˚C)

This is because weaker Se-Cl bond (vs S-Cl) allows reaction to proceed at lower T

Question 2

Sulfoxides undergo [2,3]-rearrangements, how do selenoxides differ?

Answer 2

They occur at a lower temperature because of weaker C-Se bond

Question 3

Give the mechanism of the following selenoxide [2,3]-rearrangement

Answer 3

Question 4

What is important to remember about [2,3]-rearrangements?

Answer 4

The process is a concerted suprafacial process, as with sulfoxides

Question 5

Give the name of the following reaction

(1 equiv / 2 equiv of products formed respectively)

Answer 5

The Riley oxidation

SeO2 is useful for the allylic oxidation of alkenes to give alcohols and carbonyls

Question 6

What’re the key points of the Riley oxidation?

Answer 6

Double bond position is retained

Trans alkene favoured

SeO2 can be used catalytically if t0BuOOH is added

Question 7

Give the mechanism of the Riley oxidation

Answer 7

Question 8

Give the products of the following Riley oxidation’s

Answer 8

Question 9

Give the mechanism of the following Riley oxidation

Answer 9

Question 10

Give the mechanism of the following syn-elimination

Answer 10