Author Topic: Cl-benzene > allylbenzene > P2Pol > P2P  (Read 2061 times)

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Cl-benzene > allylbenzene > P2Pol > P2P
« on: June 10, 2002, 01:43:00 AM »
this recipe doesn't exactly use chlorobenzene, instead a
substituted chlorobenzene is used. this 2,6-dichlorotoluene
is chlorobenzene with 2 ringsubstituents(Cl & CH3) in both
ortho positions. and the other compunds below are simply
allylbenzene, P2Pol & P2P with the same 2 ringsubstituents:

   chlorobenzene  <=>  2,6-dichlorotoluene
   allylbenzene  <=>  3-(3-Chloro-2-methylphenyl)propene (17)
   P2Pol <=>  1-(3-Chloro-2-methylphenyl)propan-2-ol (18)
   P2P  <=>  1-(3-Chloro-2-methylphenyl)propanone (19)

3-(3-Chloro-2-methylphenyl)propene (17)

To a solution of the mono-Grignard reagent prepared[15] from
2,6-dichloro-toluene (48.3g, 0.30mol) in dry THF cooled in
an ice bath was added 1-bromo-3-propene (36.3g, 0.30mol).
The reaction mixture was allowed to warm to room temperature,
stirred for 15h, cooled in an ice bath, and hydrolyzed with
H2SO4/H2O (1:1) until all solids dissolved. The mixture was
extracted with ether, washed, dried, and evaporated. The
product 17 was collected as a colorless liquid at 212-214°C
upon distillation at 760 mmHg: 39.5g (79%)

1-(3-Chloro-2-methylphenyl)propan-2-ol (18)

Compound(17) (5.00g, 30mmol) was added to a solution of mercuric
acetate in water (30mL) and THF (30mL). The reaction mixture
was stirred at room temperature for 30min. Aqueous NaOH (3.0M,
30 mL) was added to the mixture followed by a solution of 0.5M
sodium borohydride in 3.0M NaOH (30mL). After the mercury had
settled, the reaction mixture was extracted with dichloromethane,
washed, dried, and evapo-rated to give a quantitative yield of
the alcohol 18 isolated as a colorless oil: 5.51g (100%);

1-(3-Chloro-2-methylphenyl)propanone (19)

Jones'reagent[17] (4.1mL) was added dropwise to a solution of the
alcohol(18) (2.00g, 10.8mmol) in acetone (50mL) cooled in an ice
bath. The reaction mixture was stirred for 2min at room tempera-
ture and diluted with water (50mL). The mixture was then extrac-
ted with ether. The organic layer was washed with water, dried,
and evaporated. The crude product was chromatographed on silica
gel using CH2Cl2:hexane 1:1 as eluent to give the ketone(19)
isolated as a pale yellow liquid: 1.20g (60%)

[15] j org chem, 1984 49: 2534; r h mitchell, y -h lai
[17] j chem soc, 1953: 2548; a bowers, t g halsall,
     e r h jones, a j lemin

j org chem, 1996 61(3): 935-940
"Synthesis and Diatropicity of trans-2',5',10b,10c-
Tetramethylfurano[3,4-e]-10b,10c-dihydropyrene. A Valence
Isomerization To Form a Novel Isoannulenofuran at the Expense
of Two Benzene and One Furan Rings"; Yee-Hing Lai, Pu Chen