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Diels-Alder Reactions of Dienes with Alkynes Catalyzed by Diazadieneiron.

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change if it were allowed to react with ketones under conditions allowing participation of the s-trans-i~omer~~~.
We have now treated (isoprene)zirconocene 9 with 3,3dimethyl-2-butanone 13. The major product (=80%) of
the thermally induced reaction (benzene, 60°C, 2 h) is the
oxazirconacycloheptene lob, which can be hydrolyzed to
give alcohols l l b and 12b. Photolysis of 9 and 13 in toluene solution leads to competitive formation of both 10b
and its isomer 10a. The amount of 10a increases as the
temperature of the photolysis is lowered (Table 1). 10a is
also formed as the major product (= 75%) in the thermally
induced reaction of (s-trans-q4-isoprene)zirconocene7 and
13 at -70°C. Upon hydrolysis, only 12a is obtained. (See
Scheme 11.)
CAS Registry numbers:
7,75361-73-8; 9, 87185-18-0; lOa, 87185-19-1; lob, 87185-20-4; Ilb, 8718522-6; 12a, 87185-21-5: 12b, 87185-23-7; 13, 75-97-8; isoprene, 78-79-5; zirconocene, 12116-83-5
121 b) U. Dorf, K. Engel, G. Erker, Organometallics 2 (1983) 462.
[3] H. Yasuda, Y.Kajihara, K. Mashima, K. Nagasuna, A. Nakamura, Chem.
Lett. 1981, 671; M. Akita, H. Yasuda, A. Nakamura, ibid. 1983, 217.
151 G. Erker, J. Wicher, K. Engel, C. Kriiger, Chem. Ber. 115 (1982) 3300.
161 G. Erker, K. Engel, J. L. Atwood, W. E. Hunter, Angew. Chem. 95 (1983)
506; Angew. Chem. Int. Ed. Engl. 22 (1983) 494; Angew. Chem. Suppl.
1983, 615.
171 G. Erker, K. Engel, U. Dorf, J. L. Atwood, W. E. Hunter, Angew. Chem.
94 (1982) 915; Angew. Chem. Int. Ed. Engl. 21 (1982) 913; Angew. Chem.
Suppl. 1982, 1974.
1
Diels-Alder Reactions of Dienes with Alkynes
Catalyzed by Diazadieneiron
By Heindirk tom Dieck* and Reiner Diercks
Dedicated to Professor Karl Winnacker on the occasion of
his 80th birthday
Diels-Alder reactions between simple dienes and alkynes proceed thermally only under somewhat drastic conditions. We have now found that iron compounds modified by 1,4-diaza-1,3-dienes (dad) 4 as directive ligands catalyze the [4 2lcycloaddition of simple dienes with nonterminal alkynes at room temperature (R in dad, see Table 1).
The same substrates yield 2 :1 adducts or 2 :2- and 1 :2-cooligomers with ligand-nickel catalystsF3].With bis(cyc1ooctatetraene)iron as catalyst, 1 : 1-adducts have been described14].
+
L
1
[Ila
CH3C[CH3)=CHCHzCR'R20H)
12a
CH~=CKH,)CH~CH~CR'R%H
I
I
13
CH3CH=C(CH3)CH2CR'RZOH l l b
+
CH~=CHCH(CH~)CH~CR'R%H 12b
R
I
R
I
R'= - C H ~ Rz= - C ( C y h
Scheme
Activator
I1
4
Table 1. Reaction of (isoprene)zirconocene 9 with the ketone 13: product ratio 10b/10a as a function of the reaction conditions.
~
A
10b
10n
+60T
+37"C
0°C
hv
-40°C
-78°C
86
14
81
19
56
44
37
63
22
78
The regioselectivity achieved [product ratio ( l l b + 12b)/
12a] was determined by gas chromatography (Table 1). In
the thermally induced reaction of 9 and 13, CC coupling
at C1 of the diene is favored by > 80/ < 20 relative to coupling at C4. When the irradiation is carried out at lower
temperatures, the pathway via the very reactive intermediate (q*-isoprene)zirconocene complexes 8 becomes increasingly i m p ~ r t a n t [ Here,
~ ~ ~ the
~~~
ketone
~ . couples preferentially with the less substituted olefin moiety. Irradiation of the reaction mixture at sufficiently low temperatures or reaction of the pure (s-trans-q4-isoprene)zirconocene isomer 7 eventually results in reversal of the observed
regioselectivity : with 22/78 the product 10a arising from
coupling at C4 of the isoprene unit, i. e. away from the methyl group, is formed predominantly.
Received: June 1, 1983 [Z 406 IE]
German version: Angew. Chem. 95 (1983) 800
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1983, 1120-1129
778
hene
Alkyne
0 Verlag Chemie GmbH, 6940 Weinheim. 1983
=
R
R
dad
5
"(dad)Feo"
+
1-3
The readily accessible complexes (dad)FeCl, 5 are activated in the presence of diene and alkyne using reducing
agents such as triethylaluminum, alkylmagnesium halides, or
magnesium-isoprene.2THF. Bis(diazadiene)iron, (dad)zFe
6c, also gives rise to an active catalyst with MEt3 at
90 "C, just as do the multicomponent systems
Fe(acac),/2dad/4AlEt3 7a or Fe(acac),/2dad/6EtMgBr
8a.
Table 1 indicates that the results depend on the substituents R on the ligand 4. Under the conditions investigated
to date, only N,W-dialkyldiazadienes are active; in contrast, N, N'-diaryldiazadienes, which are highly active in
diene cyclodimerizations, are not[". Since in the reaction of
rrans-1,3-pentadiene with 3-hexyne to afford 2 a center of
chirality is formed, complexes with chiral dad (4g-i)
were also used. Although 2 is also formed in good yield
with 5g- i, optical induction-in contrast to diene cyclodimerization using the same precatalyst"]-could not be detected.
[*] Prof. Dr. H. tom Dieck, R. Diercks
[**I
Institut fur Anorganische und Angewandte Chemie der Universitat
Martin-Luther-King-Platz 6, D-2000 Hamburg 13 (Germany)
This work was supported by the Deutsche Forschungsgemeinscbaft. R .
D. thanks the Fonds der Chemischen Industrie for a grant. Prof. A .
Krebs and Hoechst AG are thanked for samples of cyclooctyne and
trans- 1,3-pentadiene, respectively.
0570-0833/83/1010-0778 $02.50/0
Angew. Chem. hi.Ed. Engl. 22 (1983) No. I 0
absence of the alkyne, the dimerization of the diene is
usually faster than the [4+ 21cycloaddition investigated
here. A (dad)iron(q4-diene)(q2-alkyne) could be a relatively stable intermediate, whose secondary reaction to afford the cyclohexadiene complex would be the rate determining step in the catalytic reaction.
CH3
R?
- 111
"(dad)Fe*"
I
"(dad)FeO"
R'
1, R"
3, R"
=
=
R'
2
H
CH3
Table 1. Cycloaddition of dienes and alkynes R ' C 4 R ' in ether or tetrahydrofuran. Ratio of iron catalyst: diene :alkyne = 1 : 100 :100.
R'
R in
dad
Catalyst
components
Reaction with isoprene:
Et
CH(iPr)?
Me
CHfiPr)?
Et
tBu
Et
CH(iPr)?
Et
c-C,HII
Et
4-MeOC6H4
Et
2,6-MezC6H3
Et
2,6-(iPr)2C6H3
SiMe3 CH(iPr)2
Et
CH(iPr)>
Et
c-C6HI,
Et
CH(iPr)?
Et
CH(iPr)2
t
[h]
96
20
5b, 4EtMgBr 24
5a, 4EtMgBr 96
5c, 4EtMgBr 24
5d, 4EtMgBr 24
Se, 4EtMgBr 24
Sf, 4 EtMgBr 24
Sn, 4EtMgBr 48
Sa, Mg-CsHs 72
48
6c, 4AIEt3
72
la
96
8a
Sa, 4AIEt3
5a, 4EtMgBr
T
Prod["C] uct
Select./
yields [Yo] [a]
90
20
20
20
20
20
20
20
60
60
90
90
20
lb
la
lb
lb
lb
lc
lb
lb
lb
lb
82/16
97/13
96/[bI
95/33
87Ibl
-/-/-/b1/14
95/50
96/72
9 1/20
97/19
-
Reaction with trans-1.3-pentadiene:
Et
[cl
5g, 4EtMgBr
5h, 4EtMgBr
Et
[dl
Si, 4EtMgBr
Et
Iel
24
48
72
20
20
20
2
2
2
87/b1
84/49
95/64
Reaction with 2.3-dimethyfbutadrene:
6c, 4AIEt3
Et
c-C~HII
48
90
3
93/80
[a] Selectivity: mol-% 1, 2 or 3 relative to volatile products; yield relative to
diene, not optimized. @] Not determined. [c] R in dad is (R)-CH(CH,)C6H5.
[d] R in dad is (IS,2S, 3S, 5R)-3-pinanylmethyl. [el R in dad is (lR, 3R, 4s)3-menthyl.
In the presence of the catalyst, non-terminal unstrained
alkynes do not react at room temperature. Diene dimers,
which in the absence of alkynes are rapidly formed by the
catalyst, also do not arise"]; the only by-products found
were alkyne trimers in low yields and, presumably as a secondary product of the work-up, the aromatic oxidation
products of cyclohexadienes.
With the non-optimized reaction conditions given in Table 1, the conversion is 13-80%; however, in most cases
the selectivity of formation of cyclohexadiene exceeds
90%. Up to 90°C, neither cyclic dienes such as 1,3-cyclohexadiene or 1,3-cyclooctadiene nor the sterically demanding 2,5-dimethyl-2,4-hexadiene react with 3-hexyne. Experiments directed at the cycloaddition of isoprene to the
strained 4,4,7,7-tetramethylcyclooctyne led only to isolation of good yields of the benzene derivative 9 as sole
productfg1.
D,"(dad)Feo"
UI Ether,
60°C
- x /
Whereas with phosphanenickel catalysts the alkyne cooligomerization substrate of the diene is incorporated into
the product after formation of the C8 chain13], with the
(dad)iron system a normal, z. e., unstrained, alkyne apparently prevents attack by a second diene molecule. In the
Angew. Chem. Inl. Ed. Engl. 22 (1983) No. 10
Received: June 6, 1983 [Z 407 IE]
German version: Angew. Chem. 95 (1983) 801
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1983, 1138-1146
CAS Registry numbers:
la, 72985-36-5; lb, 87226-79-7; lc, 87226-80-0; 2, 87226-81-1; 3, 81226-822; Sa, 87226-73-1; Sb, 87226-74-2; Sc, 87226-75-3; Sg, 87226-77-5; Sb,
87249-26-1 ; Si, 87226-78-6; 6c, 87226-76-4; 9, 87249-27-2; isoprene, 18-79-5;
trans-l,3-pentadiene, 2004-70-8; 2,3-dimethyl-1,3-butadiene,513-81-5; dimethylacetylene, 503-17-3; diethylacetylene, 928-49-4; 4,4,7,7-tetramethylcyclooctyne, 20965-37-1; iron(rr) chloride, 7758-94-3
[l] Diazadienes as Directive Ligands in Homogeneous Catalysis, Part 6.Part 5: H. tom Dieck, I. Dietrich, Chem. Ber., In press.
131 P. W. Jolly, G. Wilke: The Organic Chemistry of Nickel. Academic Press,
New York 1975, Vol. 2, p. 167; W. Keim, A. Behr, M. Roper in G. Wilkinson, F. G. A. Stone, E. W. Abel: Comprehensive Organometallic Chemrstry, Pergamon Press, London 1982, Vol. 8, p. 371; P. W. Jolly, ibid. p649.
141 A. Carbonaro, A. Greco, G. Dall'Asta, J Org. Chem. 33 (1968) 3948; J .
Organornet. Chem. 20 (1969) 117.
191 The trimerization on Pd" has also been described by A. Krebs and K.-D.
Seidel; A. Krebs, personal communication.
27A1-NMR Spectroscopy: A Probe for
Three-, Four-, Five-, and Sixfold Coordinated
A1 Atoms in Organoaluminum Compounds
By Reinhard Benn*, Anna Rufiriska, Herbert Lehmkuhl,
Ed0 Janssen, and Carl Kriiger
27Al,like '*B and "B, is suitable for NMR investigations
of organometallic compounds of the 3rd main group elements because of its sensitivity and relatively favorable ratio of line width to spectral range. On the basis of the different chemical shifts 6(27Al)of octahedrally and tetrahedrally coordinated aluminum salts, it has been assumed[']
that a connection exists between 6(27Al) and the ligand
symmetry at the metal. We show here that, in general, a
simple correlation exists between coordination number
and 6("Al) in organoaluminum compounds and that this
can be used as an analytical aid to detect tri- and the much
discussed pentacoordination['] of A1 atoms.
The NMR parameters of typical compounds together
with their respective coordination number (C. N.j are given
in Table 1. In contrast to earlier postulates['], the high 6values of compounds 1-3 can be attributed to the tricoordination of the Al atom and not to substituent effects. In
the dimeric compounds 4-6 the chemical shifts of the tetrahedrally coordinated A1 atoms are found at approximately 153 ppm. With larger alkyl ligands (6) or higher degrees of association (7, lOa), the linewidth increases
markedly. Replacement of the terminal alkyl ligands by
groups having a-heteroatoms can substantially alter
S('7Al), e.g., 140 for (EtAlC1z)2and 95 for (C13Al)2.In contrast, ~ 5 ( ~ ' Afor
l ) compounds (4-11) with tetracoordination is apparently insensitive to the type of ligand involved
in the multicentered bonding. Ligands which have two do[*] Dr. R. Benn, Dr. A. Rufiriska, Prof. Dr. H. Lehmkuhl, E. Janssen,
Prof. Dr. C. Kriiger
Max-Planck-Institut fur Kohlenforschung
Postfach 01 1325, D-4330 Miilheim a. d. Ruhr 1 (Germany)
0 Verlag Chemie GmbH. 6940 Weinheim, 1983
0570-0833/83/1010-0779 $02.50/0
779
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