Chemistry Reference
In-Depth Information
3,3
0
,2,2
0
-tetramethoxy-1,1
0
-biphenyl and proceeding via 846 has been described.
Carbonylation of 846 using (1R,2S,5R)-(
)-menthyl chloroformate 847 affords the
dicarbonate intermediate 848 in 88% yield [622].
C
O
O
O
O
Cl
O
847
OH
OH
O
O
O
O
Et
3
N
benzene
rt, 1 h
848
88 %
O
O
O
846
O
O
Br
OH
Br
OH
Br
OH
Br
OH
O
O
(M)-
(P)-
849
849
Typical procedure. 1,1
0
-Biphenyl-2,2
0
-diyl-O,O
0
-bis[5-methyl-2-(1-methylethyl)cyclohexyl)]
carbonic ester 848 [622]:
A solution of 846 (2.10 g, 8.50 mmol) and triethylamine
(2 mL) in benzene (15 mL) was added dropwise to a solution of (
)-(1R,2S,5R)-
menthyl chloroformate 847 (4.10 g, 18.76 mmol) in benzene (15 mL) at room
temperature under N
2
. The solution was stirred at room temperature for 1 h,
washed with 10% aq. HCl and water, and the organic phase was diluted with di-
chloromethane. After drying over Na
2
SO
4
, evaporation of the solvent left a color-
less solid, which was purified by flash chromatography using CH
2
Cl
2
/petroleum
ether (1:1) as eluent to give 848 (4.57 g, 88%); mp 202-204
C.
Modern generations of insecticides continue to take advantage of the toxicity
to insects of a particular halogen substitution pattern in the molecule and also
contain functionalities guaranteeing ready degeneration by environmental agents.
An example is the 2,2-dichlorovinyl unit in pyrethrin analogues [623, 624]. In
this context, 2,2-dichlorovinyl neopentyl carbonate 852 has been prepared via 1,2,2,2-
tetrachloroethyl neopentyl carbonate 851 by reaction of neopentyl alcohol 850 with
1,2,2,2-tetrachloroethyl chloroformate and reduction of the resulting product 851
with zinc dust [58].
C
