Synthese makrocyclischer Lactone durch Ringerweiterung. Vorläufige Mitteilung

Angew. Chem. Int. Ed. Engl. 12 (1983) It is not surprising that the use of transition metals to modify carbanion reactivity was at first not considered. Indeed, for a long time, the only isolable complexes with carbon-transition metal o bonds (~l'-complexes)"~~ were copper([) compounds with d"-configuration of the metal and the corresponding Pt-and Au-derivatives. The reason for this is that so-called p-H-abstraction [reaction (I), reductive elimination] is much faster with alkyl-transition metal compounds than with the equivalent main-group metal compounds. In addition, oxidative dimerization of two organic residues (with concomitant reduction of the metal) occurs at a transition metal center much more readily [reaction (2) Complexes which owe their stability to having alkyl groups without b-hydrogen atoms [Rule (a)] are of interest to the inorganic chemist for the investigation of the structural and thermodynamical properties of the transition metal-carbon bond. Even should a preparative method emerge from these investigations, however, the restriction to such systems would be a severe limitation. Thus it is the possibilities mentioned under b), c), and d) which are of consequence in the search for sufficiently stable organotransition metal reagents for organic synthesis. Properties of Organo-titanium and -zirconium Compounds without Cyclopentadienyl LigandsAim and Limits of the ReviewIn 1952, Herman and NeIson['81 described phenyltitanium isopropoxide as the first compound with a carbon-titanium o bond"'] (Scheme 1). Two further discoveries at the same time stimulated the development of organotitanium chemistry: the synthesis of ferrocene by Kealy and Pauson[201, and the observation by ZiegIer et aZ.[2'1 that titanium compounds in mixtures with alkylaluminum compounds are extremely active catalysts for the polymerization of olefins.After elucidation of the structure of f e r r o~e n e [~~-~'~, cyclopentadienyl-titanium and -zirconium halides 2 were some of the first compounds to be prepared by the action of cyclopentadienylmagnesium halides on transition metal salts, and from which the o-derivatives of type 3 and 4, which have until recently dominated the picture in organic synthesis, are derived'251. As a result of the work of Herman and complexes of the general type 5 have been systematically synthesized mostly for the purpose (as with the Cp-derivatives) of investigating the catalytic effect on olefin polymerization. The chloro derivatives 5 , X =el, proved to be rather unstable expect in the absence of easily-abstractable P-ligands, and the stability decreased markedly with increasing degree of alkylation. On the other hand, the alkoxy and, especially the dialkylamino complexes 5 , X=OR' or NR;, showed a thermal stability which was sometimes fully comparable with that of the Cp-derivatives[26J.The alkoxy and aryloxy derivatives 5 , X=OR', n = l were chosen for the first investigations in our group on the use of organo-titanium and -zirconium compounds for the following reasons:Angew. Chem. In#. Ed. Engl....

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“…Some examples of reactions with substrates having functionality additional to the aldehyde gr0up139. 49,501 are shown in Scheme 3. …”

Section: Preparation Of (R'o)tir (R'o)andr and (R;n)tir Compounds Imentioning

confidence: 99%

Organometallic Compounds of Titanium and Zirconium as Selective Nucleophilic Reagents in Organic Synthesis

Weidmann

Seebàch

1983

Angew. Chem. Int. Ed. Engl.

275

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“…J = 6,2, CH3-C(I) (Einstrahlung hei 4.71)). "C-NMR: 219,5 (s, C(2')); ,5; 33.2; 32,6; 28,3; 27,6; 27S; 27,3; 25,7; 25,53; 25,47; 25,l; 24,8 (2 C); 19,8, 19,6 (24, CH,-C(1)); 14,2 (9, 125 (7) (2)); 42,l;41,9;37,l;36,Y;33,O;3 2 3 ;28,7: 28,4;27,4;27,3;2 5 3 ;25.7;25,6;25,5;24.8;23,5;23,4 (24,CHI). ELMS: 198 (2, M+'), 183 (21, 180(18), 151 (20).…”

mentioning

confidence: 98%

“…Zur Synthese makrocyclischer Lactone wurden bisher als elektronenanziehende Gruppen NO, [3] [4], C,H,SO, [5] und CN [6] verwendet. Als weitere funktionelle Gruppe, die fur die angegebene Reaktionsweise in Betracht zu ziehen ist, kommt die Alkoxycarbonyl-Gruppe in Frage.…”

unclassified

Eine neue Synthese von (±)‐Dihydrorecifeiolid

Milenkov

Hesse

1986

Helvetica Chimica Acta

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A New Synthesis of ( f )-DihydrorecifeiolideEthyl I-(2'-formylethyl)-2-oxocyclooctane-l-carboxylate (2) prepared by Michuel reaction of ethyl 2-0x0-cyclooctane-I-carboxylate (1) was regioselectively methylated at the aldehyde group with (CH,)2TI[OCH(CH3)2]2 to give 3 (Scheme, 1 ) . The alcohol 3 was trcatcd with Hu4NF to give the deethoxycarbonylated product 4 which by distillation gave the bicyclic enol ether 5. Oxidation (m-chloroperbenzoic acid) of 5 and reduction of the resulting oxolacton 6 yielded the title compound ( + )-dihydrorecifeiolide (7) in an overall yield of nearly SO %. Methylation of the aldehyde 2 with MeLi gave the ring-enlargcd lacton 9 in poor yield (13%). The deethoxycarbonylation reaction 3 + 4 was studied in more detail (Scheme 3).

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“…Im folgenden berichten wir uber eine einfache Synthese, die von 2-Nitrocyclohexanon (2) ausgeht und uber das bicyclische 5-Nitrobicyclo[3.3.l]nonan-2,9-dion (3) verlauft, welches durch Hydrolyse in quantitativer Ausbeute 1 ergibt.…”

unclassified

“…2-Nitrocyclohexanon (2) 121 liess sich rnit Acrylaldehyd in Gegenwart von Ph,P zu 3-( 1 -Nitro-2-oxocyclohexyl)propanal (4) umsetzen [3]. In Gegenwart von NaH reagierte 4 M = 197,Schmp.…”

unclassified

Synthese von Bicyclo[3.3.o]oct‐1(5)en‐2‐on aus Cyclohexanon

Lorenzi-Riatsch

Nakashita

Hesse

1984

Helvetica Chimica Acta

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Synthesis of Bicyclo[3.3.0Joct-l(5)en-2-one from Cyclohexanone SummaryTreatment of 2-nitrocyclohexanone (2) with acrylaldehyde yielded in the presence of tetrabutylammonium fluoride the bicyclic product 5, which was oxidized to the nitro-diketone 3. The conversion of 3 to the title compound 1 was achieved in nearly quantitative yield under unusual conditions: K,CO,/H,O and H,SO,. Compound 3 was also converted to 1 (stepwise and one-pot reaction, respectively) by treatment with 1. NaOCH,, 2. TiCl,, and 3. H,SO, (Scheme).

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Synthese makrocyclischer Lactone durch Ringerweiterung. Vorläufige Mitteilung

Cited by 30 publications

References 11 publications

Organometallic Compounds of Titanium and Zirconium as Selective Nucleophilic Reagents in Organic Synthesis

Organometallic Compounds of Titanium and Zirconium as Selective Nucleophilic Reagents in Organic Synthesis

Eine neue Synthese von (±)‐Dihydrorecifeiolid

Synthese von Bicyclo[3.3.o]oct‐1(5)en‐2‐on aus Cyclohexanon

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