Methyl lithioacetate

The major limitation on the reactivity of cycloheptadienyliron complexes is the fact that treatment with hard enolates, such as methyl lithioacetate results in deprotonation to give, e.g. the V-triene complex (89). This appears to be less of a problem in the corresponding cyclohexadienyl systems. 

The tricarbonyliron-coordinated cyclohexadienylium salts are readily available on a large scale by azadiene-catalyzed complexation of the corresponding cyclo-hexadienes with pentacarbonyliron [23] and subsequent hydride abstraction using trityl tetrafluoroborate [24]. Alkylation of methyl lithioacetate with the iron complex... 

Fukuyama and Yung (81TL3759) used adduct 69 as a key starting material for the synthesis of methyl ( )-3-(3-cyana-6-oxabicyclo[3.I.0]hex-2-en-5-yl)-2-propenoate (81). The reaction of cycloadduct 69 with methyl lithioacetate gave unsaturated ester 77. Reduction in acidic media of the conjugated double... 

Chiral allylation of imines by an allylstannane is promoted by a bis-Ji-allylpalladium complex based on the pinane skeleton, while using triallylborane to supply the allyl group a polymer-supported arenesulfonaminoisobomeol can provide a proper environment. The chirality of alkenyl sulfoxides imposes the approach of methyl lithioacetate, and therefore it enables the generation of optically active P-amino acids. ... 

Carbon nucleophiles of type (iii) add to the arene ligand and do not rearrange examples include the very reactive anions, such as 2-lithio-2-methyl-l,3-dithiane, and the less sterically encumbered anions, such as lithio acetonitrile and /-butyl lithioacetate. In these cases, the anion adds to an unsubstituted position (mainly ortho or meta to Cl, as in 22) and does not rearrange. Then iodine quenching, even after a long period at 25 °C, gives almost exclusively the products from formal substitution for hydrogen, as from (22) in Scheme 8. 

Selectivity is more complicated with a methyl or chloro substituent. Again, meta substitution is always significant, but ortho substitution can account for 50-70% of the mixture in some cases [2]. More reactive anions (1,3-dithianyl) and less substituted carbanions (e.g., tert-butyl lithioacetate) tend to favor ortho substitution. Representative examples are shown in Table 3. Entries 2-4 show that variation of reaction temperatures from -100 °C to 0 °C has no significant effect in that highly selective system. The added activating effect of the Cl substituent allows addition of the pinacolone enolate anion (entry 11), whereas no addition to the anisole nor toluene ligand is observed with the same anion. 

Ethyl-2-fluorobenzothiazolium tetra-fluoroborate, 223-225 Ethyl indolepropionates, 313-314 Ethyl ketals, 262 Ethyl lactate, 298 Ethyl lithioacetate, 225 Ethyl malonate, 311 Ethyl mandelate, 298 Ethyl mesityl ketone, 295 Ethyl methyl ketone, 340 N-Elhyl-5-phenylisoxazoiium 3 -sulfonate, 226... 

In contrast, Michael additions of a,a-disubstituted lithium enolates proceed, apparently via the chelated form of enone sulfoxides (Figure 5.2), with almost complete jt-facial diastereoselectivity [104]. This methodology has been used in the asymmetric synthesis of the pheromone, (-)-methyl jasmonate (121), from cyclopentenone sulfoxide (98b) [105] via the intermediate (120), which was formed in at least 98% enantiomeric purity upon asymmetric Michael addition of bis a-silylated a-lithioacetate to (98b). Addition of the a-bromo enolate (122) to enantiomerically pure (98a) and oxidation gives the product sulfone (123), with almost complete asymmetric -induction with respect to the sulfoxide. Sulfone (123) was then converted into the steroidal sex hormone, (+)-oestradiol (124) (Scheme 5.42) [106]. 

Related Reagents. f-Butyl a-Lithiobis(trimethylsilyl)acetate f-Butyl Trimethylsilylacetate Ethyl Bromozincacetate Ethyl Lithioacetate Ethyl Trimethylsilylacetate Ketene Bis(trimethyl-silyl) Acetal Ketene f-Butyldimethylsilyl Methyl Acetal l-Methoxy-2-trimethylsilyl-l-(trimethylsilyloxy)ethylene Methyl (Methyldiphenylsilyl)acetate Methyl 2-Trimethylsilyl-acrylate Triethyl Phosphonoacetate Trimethylsilylacetic Acid. 

A Michael addition of the silyl enolate was employed in a short synthesis of ( )-methyl jasmonate from cyclopentenone (eqs 9 and 10). This convergent scheme was carried out in three steps conjugate addition of methyl Q -(methyldiphenylsilyl)lithioacetate to cyclopentenone, alkylation of the resulting enolate with (Z)-l-bromopent-2-ene, and desilylation with potassium fluoride ( )-ethyl jasmonate was prepared in a similar fashion. In the conjugate addition step, the Q -(methyldiphenylsilyl)ester gave superior results to those obtained with the a-trimethylsilyl esters. 

Related Reagents. t-Butyl a-Lithiobis(lrimethylsilyl)acetate t-Butyl Trimethylsilylacetate Dilithioacetate Ethyl Bromozin-cacetate Ethyl Lithioacetate Ethyl Lithio(trimethylsilyl)acetate Ketene Bis(trimethylsilyl) Acetal Ketene t-Butyldimethylsilyl Methyl Acetal l-Methoxy-2-trimethylsilyl-l-(trimethylsilyloxy)-ethylene Methyl (Methyldiphenylsilyl)acetate Trimethylsilyl-acetic Acid. 

Related Reagents. t-Butyl a-Lithioisohutyrate Dilithio-acetate Ethyl Lithioacetate Ketene Bis(trunethylsilyl) Acetal Ketene f-Butyldimethylsilyl Methyl Acetal l-Methoxy-l-(tri-methylsilyloxy)propene l-Methoxy-2-trunethylsilyl-l-(tri-methylsilyloxy)ethylene Tris(trimethylsilyloxy)ethylene. 

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