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Michael Additions of Metalated Thioacetals to Cyclic Enones.

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Experimental :
( 5 a ) and ( 6 a ) : BCI3 (15g, 0.13mol) is condensed into a
solution of (R3Si)2NPNSiR3(28g, 0.1 mol) in light petroleum
(100ml) contained in a 250-ml two-neck flask fitted with two
reflux condensers ( - 70°C), moisture being rigorously
excluded. The reaction mixture is then stirred for 1 h with
cooling (< - 10°C). After removal of the solvent and R3SiCI
in a water-jet vacuum at room temperature, the volatile fraction (up to !2O0C/O.1 torr)['] is separated from the polymeric
component of the reaction mixture. Lower boiling fractions
(up to 4O0C/O.1 torr)['] are collected separately and fractionated over a "slit-tube" column[81at 1.0 torr. (5a)['] (7g,
25 %) is obtained at 41-42"C, and ( 6 a ) l 9 ](3g, 12%) at 4647°C.
( 5 b ) : BBr3 (15g, 0.06mol) is added dropwise with stirring
to (R3Si)2NPNSiR3(14g, 0.05 mol) under an inert gas at 0°C.
After 1 h at room temperature most of the R3SiBr is drawn
off and the residue is fractionated in an oil-pump vacuum.
Redistillation (Vigreux column) of the fraction obtained at
50-65 "C/O.l torr affords ( 5 b)I9] (1 3 g, 70
b. p. 6061 OC/O.l torr.
(stanny1)methanes (I) undergo 1,4 addition to cyclic enones
(2) in good yields-in contrast to the corresponding 1,3-dithiane derivatives which only undergo 1,2 additionI4l. The resulting enolates (3) afford the Michael adducts (41, E = H, on
aqueous work-up. However, the enolates can be alkylated
directly by treatment of the reaction mixture with alkyl iodides
to form the a$-disubstituted ketones ( 4 ) , E # H , which are
isolated predominantly as trans isomers: (For examples, see
Table 1.)
0
(a),
M
= Si
( b ) , M = Sn
z),
OLi
0
(3)
(4)
Received: July 25, 1974 [Z 109 IE]
German version: Angew. Chem. 87.34 (1975)
0Li
[ I ] 1. Huiduc: The Chemistry of Inorganic Ring Systems. Wiley-Interscience,
London 1970, pp. 124, 805.
123 E. Niecke and W f l i c k , Angew. Chem. 86, 128 (1974); Angew. Chem.
internal. Edit. 13, 134 (1974).
[3] E. Niecke and W Flick, Angew. Chem. 85, 586 (1973); Angew. Chem.
internat. Edit. 12, 585 (1973); 0. J. Scherer and N . Kuhn. Chem. Ber. 107,
2133 (1974).
[4] The formatlon of bis(trimethylsilyl)aminodibromophosphane ( 6 b ) could
be detected only by N M R spectroscopy: 6,,=
-0.44 ppm, 4J,,=2.5 H z ;
hP=
-213ppm.
[S] Based on the isotopes "B, 35CI,and '"Br.
[6] The missing ring vibration occurs in the range 720-790cm-'.
[7] The higher boiling component contains a solid, presumably
bis(trimethylsilyIdichloroborylamino)chlorophosphane,which has not yet
been isolated pure.
[8] "Spaltrohr" column, Fischer. Labor- und Verfahrenstechnik, Bonn-Bad
Godesberg.
[9] Co. 95'X pure. The amount of trimethylsilyl halide present owing to
decomposition on distillation is 3-5 %.
Michael Additions of Metalated Thioacetals to Cyclic
Enones[**]
By Dieter Seebach and Ruiner Burstinghaus"]
The Michael addition of nucleophilic acyl equivalents to a$unsaturated carbonyl compounds [eq. (I)] is a reaction of
particular synthetic utility[''.
So far this transformation has succeeded in the case of thioacetals as masked acyl anions only on use of lithium cuprates" h. ".
To our surprise, we have now found that the readily accessible[3a1lithiated bis(methylthio)(silyl)- and bis (methylthi0)[*I Prof. Dr. D. Seebach and DipLChem. R. Burstinghaus
lnstitut fur Organische Chemie des Fachbereichs 14 der Universitat
63 Giessen, Ludwigstrasse 21 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
(Projects Se-158-6 and Se-158-10) and the Fonds der Chemischen Industrie.
Anyew. Chrm. internat. E d i t .
Vol. 14 ( 1 9 7 5 ) 1 N o . I
Table I . Yields of ketones ( 4 ) prepared from thioacetals ( I ) and enones
(2).
M
n
R
E
Yield
['XI
Si
Sn
Si
Si
Sn
Si
Sn
Sn
Si
Sn
Si
2
2
2
2
2
3
3
3
3
3
4
H
H
CH 1
n-C7H I 5
n-CqHII
H
H
H
CH 3
H
H
[a1
73
70
71
65
65
78 [bl
75
65
75
60
60
[a] Products isolated by molecular distillation i n uucuo.
[b] M.p. 56°C.
Finally, in the case of the adducts ( 3 b ) it is possible to
produce the novel dilithium derivatives ( 5 ) by transmetalat i ~ n l ~as~ we
l , were able to show, e.g., by hydrolysis to the
tin-free product ( 6 ) , n = 3, E 1= E2 = H [NMR in CCI, : one
SCH, singlet at 6=2.1 ppm, 5-Hz doublet of the (RS),CH
proton at 6= 3.5 ppm]. Apparently, the carbanionoid center
adjacent to the S atoms in ( 5 ) is more nucleophilic than
the enolate system, for after addition of one equivalent of
methyl iodide and subsequent hydrolysis we isolated ( 6 ) ,
n=3, E'=CH3, E 2 = H [NMR in CCI4: two SCH3 singlets
separated by 2Hz (diastereotopic) at 6 = 2.0 ppm, (RS),C-CH,
as singlet at 6 = 1.4ppml.
To our knowledge, the compounds ( 1 b ) described above
and the corresponding 1,3-dithiane derivatives[4b1are the first
57
a-stannyl-organolithium compounds to have been prepared
by direct metalation (H/Li exchange)[5!
The sulfur-free carbonyl compounds (7), (S), and ( 9 ) have
been prepared by thioacetal hydrolysis or Raney nickel desulfurization oftheadducts ( 4 a ) . Yields: 71,66, and 60%,respectively; 'H-NMR (cc14):Si(CH3)3 singlets at 6=0.2, 0.23,
and 0.25, respectively; CH3 in ( 8 ) : 0.95 (d, 7 t h ) ; IR: 1710,
1640; 1745, 1635; and 1735, respectively.
H
R4
COCI2, pyridine
>
50 9:
R'-CH-COZ-CH,%~
I
>TICOR'
ill
J
Received: August 8. 1974 [Z 112 IE]
German version: Angew. Chem. 57, 37 (1975)
CAS Registry numbers:
( l a ) . R=CH,, 53369-90-7; ( I b ) , R = C H , , 53369-91-8;
O b i , R=n-C,H,, 53369-99-6; ( I b ) , R=C,H,, 53370-00-6;
(21, n=2,930-30-3; (Z), n=3, 930-68-7;
(2). n=4. 1121-66-0; (5), n = 3 , 53369-93-0; (6), n=3. E ' = E 2 = H ,
53369-94-1; ( 6 ) , n=3, E l = C H , , E 2 = H , 53369-95-2; (71, 53369-96-3;
(8). 53369-97-4; (9) 53369-98-5; ( 4 ) . M=Si, n=2, R=CH,, E = H ,
53370-01-7; ( 4 ) , M=Sn, n=2, R = C H , , E = H , 53370-02-8;
( 4 ) . M=Si. n=2, R = E = C H , , 53370-07-3; (41, M=Si, n = 2 . R = C H , ,
E=n-C,H,,, 53418-35-2; 141, M=Sn, n = 2 , R=CH,, E=n-C,H,,,
53370-10-8; (41, M = S i , n = 3 , R = C H , , E = H , 53370-03-9;
141, M =Sn. n=3, R=CH,, E = H , 53370-04-0; ( 4 ) , M=Sn, n=3,
R=n-C,H,,
E = H , 53370-05-1; ( 4 ) . M=Si, n=3, R = E = C H , ,
53370-08-4; (41, M = S n . n=3, R=C,H,, E = H , 53370-06-2;
( 4 ) , M=Si, n=4, R=CH,, E = H , 53370-09-5
[ I ] a) Cyanohydrin derivatives: H . Srerrrr and M . Schreckenberg, Angew.
Chem. 85.89 (1973); Angew. Chem. internat. Edit. I2,81 (1973); Tetrahedron
Lett. 1973, 1461; Chem. Ber. 107, 210 (1974): E . Leerr, M . R. Chedekd,
and G . B. Bodem, J. Org. Chem. 37. 4465 (1972). b) Cuprates of thioacetals:
7: Mukaij,ama, K. Narasaka, and M . Furusaro, J. Amer. Chem. Soc. 94,
8641 (1972). c) Anions of thioacetai monosulfoxides: R. H . Schlessinger et
af., Tetrahedron Lett. 1973,2595.2599, 2603, 3267, 3271, 3275. d ) Nitroalkane
anions: J . E . McMurry el a f . , J. Amer. Chem. Soc. 93, 5309 (1971); J. Org.
Chem. 38, 4367 (1973); 39, 258, 259 (1974). e) Carbonylnickel derivatives:
E . J. Core! and L. S. Hegedus, J. Amer. Chem. Soc. 91, 4926 (1969). f)
Anions of oxazolones: W Steglich ef a / . , Angew. Chem. 83, 725, 727 (1971);
Angew. Chem. internat. Edit. 10, 653, 655 (1971).
[2] In the Michael additions described in ref. [ l c]. further stabilized anions
derived from thioacetals are employed.
[3] a) For production of ( l a ) , see ref. [4a]. For preparation of ( I b ) ,
(CH ,S)KHLi [4] is reacted with chlorostannanes and the resulting
( C H I S ) I C H S ~ RisI metalated with lithium diisopropylamide in THFiHMPA
at -78 t o -30°C. b) Prior to transmetalation of (3) t o (5) (CH3Li at
- 100°C) the diisopropylamine is distilled off with the major portion of
the T H F (replaced later) at 0°C bath temperature and 0.001 torr pressure.
[4] a) Lithiated silylthioacetals: D. Seebach, M . Kolb, and B.-7h. GrBhel.
Chem. Ber. 106, 2277 (1973). b) Lithiated stannyldithianes: I. Wiflerr and
B.-Th. GrBbef, Universitat Giessen, 1973 (hitherto unpublished).
[S] For (R,Sn),CCI, +RLi+(R,Sn)CCI,Li, see: D. Seyferrh, F . M . Armbrechr
jr., and E. M . Hanson, J. Organometal. Chem. 10, P-25 (1967);
(R,Sn)CBr,+RLi+(R ,Sn)CBrILi: D. Sryferrh rr af., ibirl. 44, 299 (1973).
(31
(41
minutes' stirring at 20°C to 50-70°C for 1-3 hl2]. P205
in chloroform proved to be less satisfactory as reagent since
acid-sensitive allyl residues are liberated (see Table 1).
From the 'H-NMR spectra of ( 3 e ) and ( 3 f ) it is evident
that only one diastereoisomer is formed in each of these
cases; this is in agreement with the stereospecific course of the
CIaisen rearrangementl51.
On prolonged heating, the 2-oxazolin-5-ones (3), R ',R4 H,
obtained from 3,3-disubstituted ally1 esters are converted by
further hetero Cope rearrangement into 2-allyl-3-oxazolin-5ones ( 4 ) . For the preparative synthesis of (4) it is recommended that esters ( 1 ) be used as starting material, without
isolating ( 3 ) (Table 1).
The ease of the secondary reaction ( 3 ) + ( 4 ) depends on
the spatial requirements of the groups R', R3, R4. Thus ( 3 f )
rearranges completely into ( 4f ) on boiling in chloroform
for 3 h, while 12 hours' boiling in benzene is necessary for
the rearrangement ( 3 e ) + ( 4 e ) . Under the conditions used
for cyclization (COC12/pyridine, 1.5 h, SOT), N-isobutyryl-2phenylglycine geranyl ester affords (4h) directly-as a result
of additional stabilization of the 3-oxazolinone form by conjugation of the C=N double bond with a phenyl residue.
4-Allenyl-2-oxazolin-5-ones( 6 ) are accessible in the same
way as ( 3 ) if the propargyl esters of N-acyl amino acids
(5) are cyclized instead of ( 1 ) (Table 2).
+
R2
R1-CH-C02-C-C~
I
I
C,H,COHN
A3
CH
-
Hc0
R'
N v O
I
C6H5
Hetero CopeRearrangements in the Cyclization of Ally1
and Propargyl Esters of N-Acyl Amino Acids to Oxazolin-5-ones["l
By Borries Kiibel, Gerhard HoJe, and Wolfgang Steglich"]
Alkyl esters of N-acyl amino acids are converted on treatment
with dehydrating agent into 5-alkoxyoxazoles['~'I. We have
found that 5-allyloxyoxazoles ( 2 ) , formed from the N-acylamino acid allyl esters
rearrange directly under the reaction conditions to 4-allyloxazolin-5-ones ( 3 ) . Cyclization is
accomplished by dropwise addition of a solution of phosgene
(1.5 mol) in toluene to a solution of the ester ( I ) and pyridine
(3-6 mol) in chloroform and warning the mixture after 30
[*] Dr. B. Kubel, Dr. G. Hofle, and Prof. Dr. W. Steglich
Organisch-Chemisches Institut der Technischen Universitat
1 Berlin 12, Strasse des 17. Juni I35 (Germany)
[**I The work was supported by the ERP Special Fund. We thank BASF
Ludwigshafen for supplying the starting materials.
58
(61
If cyclization of the esters (1 c ) and ( 5 i ) is carried out with
P4S in 1,2-dichloroethane (24 h, reflux)[61,the 2-thiazolin-5ones (m.p. 53 and 59°C resp.)I4l corresponding to ( 3 c ) and
(6 i ) are formed in 40 % yield.
4- Isopropyl-4-linalyl-2-phenyl-2-oxazolin-5-one
( 3 f ) and 2-geranyl-4-isopropyl-2-phenyl-3-oxazolin-5-one
( 4f )
But yllithium (2.5 mmol) followed by 4-isopropyl-2-phenyl-2oxazolin-5-one (4.0g, 20mmol) are added with stirring to
a solution of geraniol (3.1 g, 20mmol) in benzene (30ml).
The mixture is stirred for one day, washed with 0.5 N HCI,
dried over M g S 0 4 and finally concentrated by evaporation
under vacuum [yield 6.1 g (86 %) ( I f ) , pale yellow oil].-A
solution of COCl2 (10.3mmol) in toluene (3 ml) is now added
slowly with stirring to a solution of the ester ( I f ) (2.5g,
AngeMs. Chem. inrernar. Edit. / Vol. 14 (1975) 1 No. I
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