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Direct Diastereoselective Alkylation of Tartaric Acid Through an Enolate.

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crystallized from benzene: yield 0.5 g (22%, relative to P),
bright yellow, highly refractive crystals, m. p. = 220°C (decamp.), readily soluble in CH2Cl2.
trans-configuration. Thus, acetone has approached the
enolate (2a) from the Re-face preferentially [see (4fl in Table I]. In contrast, the p-methoxy-benzyiation of (Za) must
Received: February 1, 1980;
publication delayed at the authors' request 12 929 IE]
German version: Angew. Chem. 93, 1079 (1981)
[I] 8. Mathiasch. M . Druger. Angew. Chem. 90. 814 (1978): Angew. Chem.
Int. Ed. Engl. 17, 767 (1978); B. Mathiasch. J. Organomet. Chem. 165. 295
(1979).
121 B . Mathiasch, Inorg. Nucl. Chem. Lett. 13, 13 (1977); J. Organomet.
Chem. 141. 295 (1977).
131 Cell data: a=1742.7(2), b = 1026.5(2), c = l627.2(2) pm, /3= 104.74(2)",
V=2815.106 pm', space group C2/c, Z=4, ~ ~ . ~ ~ ~ =p,,,=2.22
2.25, g
cm-'; 3227 reflections (A=71.069 pm) of which 512 were unobserved
( < 2u). CADCdiffractometer, R = 0.022, H atoms not considered.
[4] NMR data (in CD2C12, re!. TMS or H,P04 ext.): 'H: 6=0.55,
'J(PSnCH)= 2.6, 2J( '"SnCH)=43.4, 2J( '"'SnCH) = 45.4, 'J(SnSnCH) =
15.6 Hz; 'T: 6 = -4.28, 'J(SnC)=218, 2J(PSnC)= 11.0 Hz; "P:
6 = - 299, 'J( "'SnP) = 7 14, 'J( "%P) = 749, 'J(SnSnP)= 93 Hz.
Direct Diastereoselective Alkylation of Tartaric
Acid Through an Enolate
By Reto Naef and Dieter Seebach"'
The usefulness of (+)- and (-)-tartaric acid as chiral
starting materials (pool of chiral building blocks1l1)for syntheses would be greatly enhanced, if direct alkylation to
give (I) could be achieved. Depending upon the stereochemical course of such a process, natural products with
erythro-(I) structures['', such as piscidic acid, fukiic acid,
or loroglossine, which have hitherto been synthesized only
as (-+)-mixtures by elaborate routes, might become readily accessible in enantiomerically pure form.
We have now succeeded in finding conditions for generating lithium enolates (2a) and (2b) from (R,R)-tartrate
have occurred from the Si-face: the diastereomeric mixture
(3e)/(4e) was hydrolyzed with 0.1 N HCI (methanollwater
1 :I ) to give the dihydroxyester, the major isomer of which
was obtained by crystallization. According to the 'H- and
I3C-NMR spectra, supported by measurements in the presence of a chiral shift reagent, and comparison with an authentic
the major product is the 97% enantiomerically pure threo-isomer (6) (m. p. = 107.0- 107.5, [a]g=
- 26.3 (c=O.57, CHCI,)), while natural piscidic acid is eryfhro-(i'). By analogy, we assume that all main products of
allylation and benzylation of (2) have the trans-coniiguration (Table I), i. e. that the substitution of the a-proton of
tartaric acid occurs with retention of configuration.
Table I. Ratios of diastereorners, yields, and specific rotations of the products obtained from alkylations of (2). The yields refer to distilled samples (3)+ (41, the rotations of which are given without diastereomer enrichments.
Educt
El
(2a) Ally1 bromide
(26) Crotyl bromide
(2c) I-Bromo-3-methyl-2-butene
(20) Benzyl bromide
(2a) p-Methoxybenzyl bromide
(20) Acetone
6OOH
(Za), R = CH,
/2h), R = CH(CH3)Z
i2ci
acetonide~'~'.
Alkylation with highly reactive electrophiles
leads to pentasubstituted trans/cis-dioxolanes (3)/(4) in
yields ranging from 40 to 80% (Table 1); the diastereomeric
ratios of ca. 80 :20 can be determined from the 'H-NMR
spectra. The stability of the enolates (24 and (26). sufficient
for allylations and benzylations but not for n-alkylations,
can be rationalized by assuming, that the rigid acetonide
skeleton holds the enolate n-system and the C-0 0 bond
at an "aldol distance", perpendicular to each other [(2c)141,
thus preventing 0-elimination.
The enolate (2a) also adds to the carbonyl group of
acetone: A 4:l-mixture of a diester of (4fl and of the
lactone ester (5) (M.p.=96-97"C, [a]:= - 11.0 (c=0.95,
CHCI,)), which spontaneously crystallizes, is isolated in
6Ooh yield. The minor component (5) must be a cis-bicyclo[3.3.0] system formed from an adduct of type (3) with
[*I Prof. Dr. D. Seebach, DipLChem. R. Naef
Products (3)f (4)
Yield
I&'
[%]
(3) $4) ( c in CHCI,)
R'
65
(a) CH2CH=CH2
(b) CH2CH=CHCH, 46
(c) CH2CH=C(CH,)2 75
87: 13
78 :22
82 : I 8
- 19.1" (1.52)
- 16.7" (1.08)
(d) CH2C6HS
(el p-C,HIOCH2
54
77
84: 16
82: 18
-37.8" (1.00)
-38.8" (5.58)
0) C(OH)(CH,)2
601al
0 Verlag Chemie GmbH, 6940 Weinheim, 1981
-28.8" (0.58)
+ 15.2" (2.57) [b]
[a] Total yield of (4fl and (5% ratio 4 : I . [bl Rotation value of pure (411.
Procedure
(3d)/(4d): To a solution of dimethyl (R,R)-tartrate acetonide (3.27 g, 15 m m ~ l )and
[ ~ ~benzyl bromide (3.06 g, 18
mmol) in 50 mL of tetrahydrofuran (THF)/IO mL of hexamethylphosphoric triamide, stirred under argon at - 78 "C,
is added within 30 min a solution of lithium diisopropylamide (16 mmol) in 50 mL of THF cooled at -70°C. The
temperature is allowed to rise to - 10°C over 6 h, the reaction mixture poured into 300 mL of diethyl ether, the resulting solution washed with water ( 5 x 200 ml), dried over
magnesium sulfate, and the solvent removed by evaporation. Kugelrohr distillation (165 "C/0.005 torr) gives 2.5 g
(54%) of the mixture (3d)/(4d) (84 :16) as a yellow resin.
Laboratorium fur Organische Chemie
der Eidgeniissischen Technischen Hochschule
ETH-Zentrum, Universitatstrasse 16, CH-8092 Zurich (Switzerland)
1030
( Z R , SS)-erythro-I7)
(+)-piscidic acid
n
IC-0
(4)
(2 R , 3 R ) -threo-i6)
(2)
'ENOLATE
i1)
( 3 ) [u), R' = CH,
ih), R' = CH(CH,),
Received: July 6, 1981 [Z 939 IE]
German version: Angew. Chem. 93, I 1 13 (1981)
0S70-0833/81/1212-1030 $02.50/0
Angew. Chem. Inl. Ed. Engl. 20 (1981) No. 12
[ I ] D . Seebach, E. Hungerbiihler in R. Scheflold: Modern Synthetic Methods,
Vol. 2, Salle und Sauerlander, Aarau 1980, p. 91.
121 a) A. Nordal. G. Hausfreif,J . Grether. Medd. Nor. Farm. Selsk. 28, 225
(1966); b) S . Sakamura, T. Yoshihara, K . Toyoda, Agric. Biol. Chem. 37,
1915 (1973); 33. 1795 (1969); c) R. W. Gray, A. Guggisberg, K. P. Segebarth. M. Hesse. H . Schmid, Helv. Chim. Acta 59, 645 (1976).
131 Precursor o f (2a): M. Carmack, C. J. KeNey, J. Org. Chem. 33, 2171
(1968); D. Seebach. H . - 0 . Kalinowski. 8. Bastani. G. Crass, H . Daum. H.
Dorr. N . P. Du Preez. V. Ehrig, W. Langer, C. Niissler. H.-A. Oei. M.
Schmitt, Helv. Chim. Acta 60, 301 (1977); J. A . Musich. H . Rapoport. J.
Am. Chem. SOC.100. 4865 (1978);-Precursor of (2b) by titanate catalyzed transesterification of the methyl ester: D. Seebach, E. Hungerbuhler,
R. NaeJ P. Schnurrenberger, B. Weidmann, M. Ziiger. Synthesis, in
press.
[4] Cf.: A. B. Smith. 111. P. J. Jerris, Synth. Commun. 8, 421 (1978); J. Mulzer. T. Kerkmann. Angew. Chem. 92. 470 (1980); Angew. Chem. Int. Ed.
Engl. 19. 466 (1980); J. E. Baldwin, J. Chem. SOC.Chem. Commun. 1976,
734, 736, 738.
[5] W . HeNer. Ch. Tamm, Helv. Chim. Acta 57, 1766 (1974). We thank Prof.
Ch. Tamm. Universitat Basel, for an authentic sample of dimethyl
(2R,3S)-(+)-4'-Omethylpiscidate.
Dihydrodioxetobenzodioxins:
Synthesis and Chemiluminescence"*'
By Waldemar Adam, Omar Cueto, Ernst Schmidt,
and Kiyoshige Takayama"l
In our search for novel "high-energy'' molecules for the
thermal generation of electronically excited products, we
undertook the preparation of the dioxetanes (I) derived
from 1,4-benzodioxins (4). By analogy to the perhydrodioxetodioxins (2) and the bisdioxetane (3). which on thermolysis afford electronically excited ethylene glycol diester''] and benzoic anhydrideI2],respectively, in high yield, it
was expected that electronically excited pyrocatechol diesters should be formed in high yields from 2a,8a-dihydroI ,2-dioxeto[3,4-a][I ,4]benzodioxin (])I3].
Herewith we report the preparation, characterization, and chemiluminescence of the novel dioxetanes ( I ) .
troscopically'". On heating, pure (la) quantitatively gave
the pyrocatechol diester ( 5 ~ ) 'with
~ ~ concomitant light
emission.
4)
(a), R
(51
fJ)
= Ph,
R'=H;
( b ) , R = Ph, R ' = M e ;
Ic). R = R ' = Me
Photooxygenation of 2-methyl-3-phenyl and 2,3-dimethyl- 1,4-benzodioxins, (46) and (4c). respectively, afforded
the corresponding dioxetanes (Ib)'*l and (lc)I9l which upon
heating were quantitatively transformed into the pyrocatechol derivatives (5b)'''' and ( 5 ~ ) "'I, respectively, with light
emission.
On thermal decomposition, the dioxetanes (I) chemiluminesce; however, the emission intensity was too weak to
be useful for quantitative determination of the singlet
quantum yields (a').We therefore used the energy-transfer chemiluminescence to assess the quantum yields'". The
activation parameters AHf and AS', and the singlet
(<pLpA)and triplet
quantum yields, respectively, are
collected in Table 1 .
(aTSA)
Table I. Activation parameters and quantum yields for thermolysis of the
dioxetanes ( I ) .
(10)
(Id
(Ib)
~
AHC [kcal/mol] [a]
AS' [cal/mol/K] [a]
AG+[kcal/mol] [b]
103 a:,Ph
[%I
@;>BA
(Dl+\
[%I
10 4
uJT/aJ'
23.8 f I .O
-5.If2
25.1 f 1
1.1 f 0 . 3
0.6f0.06
0.6 f 0.06
500 f 3 0 0
~~
25.1 f 1
-5.7It2
26.9 f 1
1.6f0.2
3.5f 1.3
3.5f 1.3
2200 f700
26.2 f I
-3.7 *2
27.3 f 1
0.09 0.02
0.02 f 0.0 1
0.02 0.01
200 * I 0 0
*
*
[a] Determined by isothermal kinetics using DBA-enhanced chemiluminescence. @] At 293.2 K.
R
Ph-
Ph
Photosensitized singlet oxygenation of a 0.03 M CHzClz
solution of the 1,Cbenzodioxins (4)141at - 78 " C , using polymer-bound Rose Bengal as sensitizer and a 400W sodium street lamp as radiation source['I, led to complete
consumption of the dioxins within 2 h, as evidenced by
N M R monitoring. For example, with (4a) the olefinic proton at 6= 6.41 disappeared with simultaneous appearance
of the dioxetanyl proton at 6=6.33. On heating to 20°C
this signal also disappeared; in its place an aldehydic proton-as expected for (5a)-appeared.
The dioxetane (la). was isolated by column chromatography (Florisil, - 60 "C, CH,CI,) and characterized spec[*] Prof. Dr. W. Adam, Dr. 0.Cuerto, DipLChem. E. Schmidt,
[**I
Dr. K. Takayama
lnstitut fur Organische Chemie der Universitat
Am Hubland, D-8700 Wiirzburg (Germany) (address to which correspondence should be sent)
Department of Chemistry, University of Puerto Rico
Rio Piedras, Pueno Rico (USA)
This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, the National Science Foundation, the
National Institutes of Health, as well as by the Petroleum Research
Fund.
Angew. Chem. fnr Ed. Engl. 20 (1981) No. 1 2
The activation parameters show that the dioxetanes (1)
are of comparable stability to that of tetramethyl-l,2-dioxetane (TMD)131.As expected, the disubstituted dioxetanes
(lb) and (lc) are more stable than the monosubstituted derivative (la). but there is no difference in stability due to
phenyl uersus methyl substitution. From the quantum
yields it is seen that, as with TMD, n,x* triplet states can
be selectively generated from the dioxetanes (I), i. e. all derivatives (la)-(lc) give very low yields of n,x* singlet
states. Surprising is the very low total quantum yield of
dioxetane (Ic). The possibility of introducing substituents
into the benzene ring and at the 2,3-positions should make
derivatives assessible which exhibit high singlet excitation
yields through intramolecular electron exchangef'].
Received: February 12, 1980,
in altered form July 5, 1981 [Z 924 IE]
German version: Angew. Chem. 93. I100 (1981)
CAS-Registry numbers:
(la), 79792-88-4; (Ib). 79792-89-5; (lc). 79792-90-8; (40). 5770-58-I ; (46).
79792-91-9; ( 4 ~ )79792-92-0;
.
(5a). 79792-93-1; (Sb), 79792-94-2; (Sc). 635.676.
[I] K . A. Zaklika. A. L. Thayer, A. P. Schaap. J. Am. Chem. SOC.100. 4916
(1978).
121 W. Adam, C . 4 . Cheng, 0. Cueto, I . Erden. K. Zinner. J. Am. Chem.
SOC.101. 4735 (1979).
131 W. Adam, Adv. Heterocycl. Chem. 21. 437 (1977).
0 Verlag Chemie GmbH. 6940 Weinheim, 1981
0570-0833/81/1212-1031 $02.50/0
1031
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