Arynes

Question 1

benzyne mechanism

Answer 1

nucleophile used is a strong base and can deprotonate benzene ortho to LG (RDS), gives -ve charge on benzene, kicks out LG giving benzyne

Question 2

substituent stabilisation of benzene

Answer 2

subs usually inductive through s-bonds, groups with -I effect help stabilise -ve charge

Question 3

elimination reactions for forming arynes

Answer 3

works for Cl, Br, F-benzene, react with Li, Li-X exchange, ionisation removes Li and leaves -ve charge, kicks out remaining halogen

Question 4

kobayashi reaction for forming arynes

Answer 4

benzene with good LG (OTs) and SiMe3 ortho, source of F- used to remove SiMe3 group, forms aryne and kicks out good LG, driving force = formation of strong Si-F bond

Question 5

alkene cycloaddition with arynes

Answer 5

stepwise [2+2] cycloadditions involving rotation about C-C bond