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Sulfur reagents in organic - Metzner P.

Metzner P., Thuiller A. Sulfur reagents in organic - Academic press, 1994. - 200 p.
Download (direct link): sulfarreagents1994.djvu
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I
obtained from 2-alkyl-3-sulfolenes regioselectively and with about 90% stereoselectively.
- (3)

Rl^Q
R^O-K2 ---
(4) (5)
+ -10% cis
(E.Z)-and (or)
(Z,E)-& iene
Interestingly, from these fram-2.5-disubstituted-3-sulfolenes (5), desulfonylation conditions [547] yielding stereoselectivity either (E,Z) or (E,E) conjugated dienes were found and applied to stereoselective syntheses of insect pheromones (including (2)).
. AcONa
or
LiAlH4/ether
reflux
R2 -
2
A. K2C03
EtOH 125C. sealed tube
(3)
The observed stereospecificity of the reductive desulfonylation of (5) by LiA1H4 in refluxing ether is also of particular interest.
The direct alkylation of 3-sulfolene followed by thermal extrusion of sulfur dioxide led [548] to a convenient synthesis of (?)-l,3-butadienyl(tributyl)stannane.
f=\ LHMDS, n-Bu^nl
so2
THF. -78C, 5 48-55%
cv
so2
<e>
Sn-n-Bu3
xylene, pyridine
reflux. 5h 45-50%
Sn-n-Buo
2-Tributylstannyl-2,5-dihydrothiophene-S,S-dioxide
To a -78C solution of sulfolene (5.0g, 42.3 mmol) and n-Bu3SnI (6.0ml,
21.1 mmol) in anhydrous THF (150ml) under argon was added LHMDS (1.0 in hexane, 29.6 mmol) in one portion. The resulting mixture was stirred for 5 min and quenched by addition of saturated aqueous NH4C1 (100ml). The mixture was diluted with EtzO (150ml) and the aqueous phase was extracted with Et20 (3x 100ml). The combined organic extracts were washed with brine (2 X 150 ml), dried (MgS04), and concentrated under vacuum. Purification by flash chromatography on silica gel (eluent: petroleum ether/EtOAc 19:1) afforded (6) (4.3g, 50% yield) as a colourless oil.
From [548] with permission.
(E)-l,3-Butadienyl(tribuiyl)stannane
A solution of the sulfolene (6) (6.5 g, 15.9 mmol), pyridine (15 ml) and a catalytic amount of hydroquinone in xylene (350 ml) was refluxed for 6h. After being cooled the volatiles were removed and the residue filtered through a short pad of deactivated (5% Et,N) silica gel using petroleum ether to yield the diene (7) (2.5 g, 47%), b.p. 97-95C/0.2 torr.
From [548] with permission.
The higher homologue of 3-sulfolene, 2,7-dihydrothiepin-1,1-dioxide could be similarly metallated at low temperatures. Reaction with reactive electrophiles followed by extrusion of sulfur dioxide led [549] to the corresponding hexatriene derivatives, as in the stereoselective synthesis of (Z,?)-l,3,5-decatriene (considered as an undecatriene in the publication) shown here.
77%
(isomeric purity > 97%)
These direct metallation-alkylation reactions of sulfolene and dihydrothiepin dioxide are incentives for future new synthetic applications of the associated cheletropic processes.
Cheletropic elimination of sulfur dioxide from benzo(c)-l,3-dihydrothiophene dioxide (8) was used as a route to o-quinodimethanes [550].
so2
dienophlles
Diels-Alder
adducts
(8)
on that methodology, Oppolzer [551] and Nicolaou [552] devised procedures for the total synthesis of aromatic steroids as (+)-estradiol and ()-estra-l,3,5(10)-triene-17-one. In this latter case, experimental conditions for the pyrolytic step are given.
mixture of 2 diastereomers
()
racemlc estratrienone
()-Estra-l ,3,5 (W)-triene-l 7-one
The sulfone (9) (mixture of two diastereoisomers, 318 mg, lmmol) was dissolved in di-n-butyl phthalate (1.62 ml) and degassed with argon. The solution was heated at 210C under argon for 8h (TLC monitoring). The reaction mixture was purified by medium-pressure column chromatography (silica, 3% ether in benzene), followed by recrystallization (hexane), to yield the product as a white crystalline solid (215 mg, 85%), m.p. 109-110C.
From [552] with permission.
For a complete coverage of the chemistry of cyclic sulfones, see [109].
References
1. E. J. Corey, Angew. Chem., Int. Ed. Engl. 30,455 (1991).
2. D. Seebach, Angew. Chem., Int. Ed. Engl. 29,1320(1990).
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