Exercício de Química Sintética e Organica Mista (460)

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17.37 (a) Friedel–Crafts acylation of benzene with benzoyl chloride is a direct route to benzophenone.
(b) On analyzing the overall transformation retrosynthetically, we see that the target molecule
may be prepared by a Grignard synthesis followed by oxidation of the alcohol formed.
In the desired synthesis, benzyl alcohol must first be oxidized to benzaldehyde.
Reaction of benzaldehyde with the Grignard reagent of bromobenzene followed by oxidation
of the resulting secondary alcohol gives benzophenone.
(c) Hydrolysis of bromodiphenylmethane yields the corresponding alcohol, which can be oxi-
dized to benzophenone as in part (b).
(d ) The starting material is the dimethyl acetal of benzophenone. All that is required is acid-
catalyzed hydrolysis.
2H2O
H�
Dimethoxydiphenyl-
methane
C6H5CC6H5
OCH3
OCH3
C6H5CC6H5
O
BenzophenoneWater Methanol
� 2CH3OH�
C6H5CHC6H5
H2O
Bromodiphenylmethane Diphenylmethanol
C6H5CHC6H5
OHBr
oxidize
C6H5CC6H5
O
Benzophenone
C6H5MgBrC6H5CH
O
1. diethyl ether
2. H3O
�
Benzaldehyde Phenylmagnesium
bromide
Diphenylmethanol
� C6H5CHC6H5
OH
PDC
CH2Cl2
C6H5CC6H5
O
Benzophenone
C6H5CH2OH C6H5CH
O
PDC
CH2Cl2
Benzyl alcohol Benzaldehyde
C6H5MgBr�C6H5CHC6H5
OH
C6H5CC6H5
O
C6H5CH
O
Benzoyl chloride Benzene Benzophenone
CCl
O
�
AlCl3
C
O
ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP 455