4c Flashcards
what type of reaction is the vilsmeier haack formylation
its when an electrophile reacts with an e- rich aromatic
when is an aromatic normally e- rich
when its a 5 membered ring
if the vils haack formylation is a rea when an electrophile reacts with an electron rich aromatic,, what must be the reagents
a 5 membered aromatic thats e- rich : 5 member ring with N or S
DMF POCl3
acidic workup
describe everything needed for the Vilks haack formylation and describe the mechanism
e- rich aromatic heterocycle
POCl3 + DMF ( di methyl formaldehyde looking thing)
the lone pair on N in DMF go up into the O which attacks the P and moves the e- onto the O of P=O. to form O-.
the O- then uses its e- to kick off a Cl on the POCl3.
the Cl - we kicked off then attacks the C=N of the DMF and the e- get carried onto the N. to neutralise it bc it was (+).
the lone pair on N then kicks off the POCl2 bit as its a good LG. to give an imine as one of the products.
H C NMe2 Cl ,, the N is (+)
the aromatic then attacks the electrohpilic C=N bond,, H is removed to make it aromatic again,, N: is used to kick off Cl,, H2O is used to attack the C=N,,, OH kicks off NMe2 and u get a formyl group on the aromatic
describe the immine formed from the beginning of vilks haack reacrion and the driving force of the reaction and its properties
immine formed =
H C NMe2 Cl
C-Cl = very weak
nucleophile can attack the C=N to give its e- to the N,, the N(-) can then be used to kick off the Cl.
when the imine binds to the e- rich aromatic,, what do we need to do
remove H to regain aromaticiry
remove Cl
add water to form a formyl group and kick off NMe2
describe the mannich reaction (dialkyl amino methylation) ,, what reagents do we need and what type of rea is this
electrophile and an e- rich aromatic!!
u need an e- rich aromatic ( usually 5 members)
Me2NH,, COH2, Me-I, Na and H+
NMe2H and formyl makes an immine,, the aromatic attacks the C=N using either alpha or beta carbon
H is removed to regain aromaticity,, NMe2 is turned into NMe3 using Me-I.
Na is added to give an aromatic with an Na attached where the NMe3 was.
when its a single haterocycle thats e- rich aka 5 members,, where do we add the subs
alpha C
when its the fused aromatics,, where do we add the substituent
on the beta carbons!!!
what about nucleophiles with e- poor aromatics,, what do we do
we substitute a halogen // good lg
we do an SNAR reaction // addition elimination reaction!!
we think which halogen /// lg is most likely to be attacked by looking at the double bonds and the series. then we attack this C,, move the e- onto an EWG . then use the EWG to kick off the original substituent.
describe the series of groups from most likely to be substituted off a e- poor aromatic!! the group with better electrophilicity will be the one one that gets kicked off. aka will be attacked,, makes sense.
F- > Cl- > Br- > I- .
whats a good lg
halides // N2 ,, NO2,, SO3R
does nucleophile with e- poor group always just give one product
nope
u sometimes get more!!
depends on how many EWG // electronegative atoms u can move the e- onto using the arrangement of the double bonds!!.
u can put it on an N,, a carbonyl etc etc!! they give the same product but there are just diff mechanisms of getting there.
