1 (988)

Prévia do material em texto

980 CHAPTER 23 
 
 
 
 
 
 
 
 
 
23.19. 
(a) We begin by identifying the bonds in compound 1 
that will be made, highlighted here: 
 
 
 
Compound A contains both an aryl bromide group and 
an aryl boronic acid group. So, disconnection of 
compound 1 at the top biaryl bond will reveal a para-
methoxy boronic acid coupling partner, while 
disconnection at the bottom biaryl bond will reveal a 
para-nitro aryl iodide partner, shown below: 
 
 
 
Now let’s consider the forward reaction sequence. 
Compound 1 is prepared from compound A via two 
successive Suzuki cross coupling reactions: 
 
 
 
Compound B (shown above) is formed via the Suzuki 
cross coupling between compound A and the para-nitro 
aryl iodide. 
 
(b) Compound A contains both an aryl bromide group 
and an aryl boronic acid group, yet it does not react with 
itself under these conditions. Rather, it prefers to cross 
couple with the para-nitro aryl iodide. This is likely due 
to the fact that aryl iodides participate much faster in 
Suzuki cross coupling reactions than aryl bromides. 
 
23.20. 
(a) First identify the carbon atoms that will be joined. 
The carbon atom connected directly to the bromide will 
be joined with the carbon atom connected directly to Zn 
in the organozinc, highlighted here: 
 
 
 
www.MyEbookNiche.eCrater.com