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Dodecamethyl-13 43-diphospha-2 3 5 6 7 8-hexastannabicyclo[2 (2).2

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kov sense. In spite of contrary predictions"'I cyclization
readily takes place, if a tertiary carbenium ion is
formed'''. The deprotonation of cyclopentyl cations (7) is
reversible so that only the thermodynamically most stable
elimination products (6) are isolated.
with phosphorus in the
Under the action of light ( I ) disproportionates to the norbornane-analogous (2)l" and dimethylstannanediyl, which
can be trapped as iodotrimethylstannane by reaction with
ZnClz (2.2 g) was dissolved in ether (2.6 mL), diluted
with 45 mL of CH2C12and cooled to - 78°C. Successively,
solutions of (3c) (5.30 g, 63.0 mmol) and (Ib) (2.64 g, 19.9
mmol) each in 10 mL of CHZCI2were added dropwise.
After 1.5 h at - 78 "C the catalyst was extracted with conc.
aqueous NH3 and the organic phase was dried over CaC12.
The crude product, obtained after evaporation of the solvent and excess alkene, was added to a solution of ZnCIz
(4.4 g) in ether (5.2 mL) and CH2C12(90 mL) at 25°C. A
stream of dry HCI was bubbled through the solution for ca.
1 min. After 35 min at 25"C, the mixture was worked-up
with aqueous ammonia as described above. Distillation
yielded 2.50 g (70%) of pure octamethylcyclopentene (6JI.
Received: July 22, 1981 [ Z 923 IE]
German version: Angew. Chem. 93, 1069 (1981)
[ ( C H ~ Z S ~ I+-~(CHdzSn:
The novel compound (1) forms as bright yellow crystals
from benzene. The X-ray structure analysis'31 indicates,
within the standard deviations, a chiral molecule with D3
symmetry (six equivalent Sn atoms, two equivalent P
atoms and six equivalent C atoms; cf. Fig. 1). The bicycle
Sn,P2 i s constructed from three Sn4P2six-membered rings
which share three bonds with each other and adopt the
conformation of a boat, twisted by 26".
[ I ] a) H. M . R . Hoffmann, Angew. Chem. 85, 877 (1973); Angew. Chem. Int.
Ed. Engl. 12. 819 (1973); b) R . 8. Woodward. R . Hoffmann, ibid. 81. 797
(1969) and 8, 781 (1969); c) J, E. Baldwin, J. Chem. SOC.Chem. Commun.
1976. 734.
[21 a) Y. Hayakawa, K . Yokoyama, R . Noyori. J. Am. Chem. SOC.100. 1791
(1978); b) M. W . E. M . van Rlborg, R . van Doom. N. M . M . Nibbering.
Org. Mass Spectrom. 15, 152 (1980); c) H. M . R. Hoffmann,R. Chidgey.
Tetrahedron Lett. 1978. 85; d) H. Sakurai. A. Shirahafa.A . Hosomi. Angew. Chem. 91. 178 (1979); Angew. Chem. Int. Ed. Engl. 18, 163 (1979).
131 a) A. Milier. M. Moore, Tetrahedron Lett. 1980, 577; b) H. Klein. A. Erbe,
H . Mayr. Angew. Chem., in press.
[4] a) Catalyst system: H. Mayr, I . K . Halbersfadf.Angew. Chem. 92, 840
(1980); Angew. Chem. Int. Ed. Engl. 19, 814(1980); b) Rules for selective
formation of 1 : 1-addition products: H. Mayr, ibid. 93, 202 (1981). 20, 184
[5] ( 4 4 : B.p.= 55-65°C (bath)/2 torr; ' T - N M R (CDCI,): 6 = 11.92, 13.20,
22.02, 31.85, 33.4 (5 q), 40.19 (d), 50.30 (t), 71.20 (s), 118.43 (d), 140.00
[6] C. K. Ingold. J. Chem. SOC.119, 305 (1921); G. S. Hammond in M . S .
Newmnn: Steric Effects in Organic Chemistry, Wiley, New York 1956, p.
460 pp; B. Capon. S. P. McManus: Neighboring Group Participation,
Plenum Press, New York 1976, Vol. 1, p. 58 pp.
171 (3d) gives a complex mixture of 1 :I-products with (la).
[8] The 1,1,2,3-tetramethylallyl cation is, however, attacked by isobutene to
an extent of 15% at the more highly substituted end (Table I , footnote
k1)191 Analogous cyclizations of the prenyl chloride-olefin-addition products
must proceed via secondary cyclopentyl cations and were not observed
a Highly Symmetrical Cage Molecule[**'
By Martin Drager and Bernd Mathiasch"'
Dedicated to Professor Leopold Horner on the occasion
of his 70th birthday
The reaction of white phosphorus with tin hydrides can
be used to form SnP bonds"]. In addition to the phosphane, we obtained the title compound (I) by reacting
['I Prof. Dr. M. DrPger, Dr.
9. Mathiasch
Institut fur Anorganische Chemie und Analytische Chemie der Universitst
Johann-loachim-Becher-Weg 24, D-6500 Mainz (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft and
by the Fonds der Chemischen Industrie.
Angew. Chem. Int. Ed. Engi. 20 (198t) No. 12
Fig. I. Molecular structure of (1) in the crystal with average bond lengths
[pm] (P.. .Pdistances; intramolecular 518, intermolecular 371 pm) and sym98,
metry elements. Average bond- and torsion-angles I"]: Sn-P-Sn
117, C-Sn-C 107, Sn-Sn-C
109, P-Sn-C
107; PSn-SnP
f26, SnSn-PSn -62, SnSn-PSn' f 3 7 .
In solution at room temperature (I) has, on average, Djh
symmetry: The NMR signals of all the methyl groups show
a joint doublet arising from 31P-coupling[41.The coupling
constants 'J(PSnCH) and 'J(PSnC) confirm the previously
found dependence on the torsion angle of the phosphorus
lone pair of electrons and the coupling nuclei in (2)l'I.
All operations are performed under argon, using solvents saturated with Ar: Me,Sn2Cl2 (4 g, 10.9 mmol) is reduced to Me4SnzH2at room temperature by LiAIH, in 70
mL of Et20. The solution is cooled to 0 ° C and ice-water
added under stirring. The ether layer is separated off, dried
over MgS04, and poured onto white phosphorus (0.3 g, 9.7
mmol, less than the stoichiometric amount). The reaction
vessel is kept dark and immediately cooled (OOC). After
48 h the phosphorus is consumed, and the crystals formed
are separated from the EtzO solution by suction and re-
8 Veriag Chemie GmbH, 6940 Weinheim. 1981
0570-0833/81/1212-1029 $02.50/0
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
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.
(2a) Ally1 bromide
(26) Crotyl bromide
(2c) I-Bromo-3-methyl-2-butene
(20) Benzyl bromide
(2a) p-Methoxybenzyl bromide
(20) Acetone
(Za), R = CH,
/2h), R = CH(CH3)Z
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)
(3) $4) ( c in CHCI,)
(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
84: 16
82: 18
-37.8" (1.00)
-38.8" (5.58)
0) C(OH)(CH,)2
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.
(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)
( Z R , SS)-erythro-I7)
(+)-piscidic acid
(2 R , 3 R ) -threo-i6)
( 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
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diphosphate, dodecamethyl, hexastannabicyclo
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