Misc

Normally the bond to the aromatic ring is broken to give a synthon with a _________ charge on the aromatic ring as they react with __________ in ____________substitutions

negative, electrophiles, electrophilic

OH & OR groups are difficult to add to a benzene ring, so don’t disconnect them but use _______ as a starting material

phenol

To improve regioselectivity, introduce a temporary _______ group e.g.

convert an NH₂ group into a larger NHCOCH₃ group

blocking

Grignards are formed by Mg insertion into an aryl halide.

They are strong nucleophiles & react with a range of electrophiles to form C–C bonds.

Wittig reaction is the general method for making ______ bonds.

C=C

Stabilised ylides are prepared by deprotonation of a phosphonium salt, that has an EWG, Ph₃P⁺CH₂EWG w/ weak base. The EWG stabilises the carboanion formed

They:

• are unreactive to ________

• react with aldehydes to give mainly ___ - alkenes, why?

ketones, E

E is more thermodynamically stable

Stabilised ylides are prepared by deprotonation of a phosphonium salt, that has an EDG, Ph₃P⁺CH₂EDG w/ strong base. The EDG further destabilises the carboanion formed

They:

• react with ketones & aldehydes to give mainly ___ - alkenes

Z

A deprotonated phosphonate ester (________ charge) is more reactive to a ____ bond than a phosphonium ylide (neutral).

Reactions of stabilised (EWG) phosphonate ester anions w/ aldehydes/ketones

gives mainly ____ - alkenes.

negative, C=O, E