Introduction of Carbon No

1 Introduction of Carbon No. 1 by Addition of Carbenes Across Nonactivated Double Bonds 

The very first synthesis of permethric add by Farkas et al. [127] was successful in analogy to the very first synthesis of chrysanthemic acid by diazoester reaction on the diene (see Reaction scheme 51). 

The technical use of this laboratory method was claimed in several variations [128, 129, 130, 131]. Advantageously, the copper catalysts may be substituted by rhodium 

More reactive is the monoolefine 94 in Reaction scheme 52. Intramolecular diazo reaction yields a precursor for the cis-permethric acid [138] (Reaction scheme 129). 

A quite different introduction of carbon-1 on the diene 93 is the oxidative addition of cyanacetic ester [139] (Reaction scheme 53). Use of CaCl2 in ethanol instead of Uthium chloride in DMF yields the cis-isomer as the main product 94. The oxidative addition of bromoacetic ester by Cu-II-acetate is a similar one [140] (Reaction scheme 54). 

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Less suited for introduction of carbon No. 1 is the carbenoid from the Simmons-Smith-reaction of diiodoacetic-ester and zinc-copper [16], and the radical addition of chloroacetic ester using cuprous chloride and bipyridyl as a radical starter [17]. 

Introduction of carbon No. 3 via carbene addition yielding chrysanthemic ester was accomplished by trapping the decomposition product 77 of methylmercapto-isopyrazole 12 with senecio ester to give 13 [23], followed by subsequent removal of the thio function with nickel (Reaction scheme 7). 

Creation of magnetic field to protect Earth from Sun s particle emission Resulted in a fixed rotational axis (no wobble) and an ever lengthening day from 5 to 24 h Creation of layers, mantle and crust Re-melting of mantle. Possibly introduction of water to give an acidic sea Introduction of carbon compounds such as amino-acids ... 

A 2-L, three-necked flask was equipped with an overhead mechanical stirrer, a Claisen adapter which contained a low-temperature thermometer, and a no-air stopper which held a gas dispersion tube for the introduction of carbon monoxide (Note 1). The flask was charged with 400 mL each of tetrahydrofuran (THF) and diethyl ether, 100 mL of pentane, and pinacolone (7.92 g, 79.1 mmol) (Note 2). The reaction solution was cooled to -110 C (Notes 3 and 4) under an argon atmosphere and carbon monoxide (Note 5) was bubbled in for 30 min. Then a solution of butyllithium (2.53 N solution in pentane, 31.0 mL, 78.43 mmol) (Note 6) was added at 0.6-1.0 mL/min by means of a syringe pump (Note 7). The reaction mixture was orange after the addition had been completed. The reaction mixture was stirred at -110°C for 2 hr while the carbon monoxide stream was continued. The liquid nitrogen Dewar was removed, and the reaction mixture was allowed to warm to room temperature over the course of 1.5 hr, during which time the color changed to yellow. 

There are no generally useful processes for the introduction of carbon substituents by electrophilic substitution of quinolines or isoquinolines, except for a few examples in which a ring has a strong electronreleasing substituent, for example 4-dimethylaminoquinoline undergoes smooth trifluoroacetylation at C-3."... 

Introduction of carbon atom No. 2 via the diazomethod is less favourable [18, 19] (reaction scheme 3) because of the non-uniform decomposition of the intermediate pyrazoline J ... 

The introduction of additional alkyl groups mostly involves the formation of a bond between a carbanion and a carbon attached to a suitable leaving group. S,.,2-reactions prevail, although radical mechanisms are also possible, especially if organometallic compounds are involved. Since many carbanions and radicals are easily oxidized by oxygen, working under inert gas is advised, until it has been shown for each specific reaction that air has no harmful effect on yields. 

Successive introduction of two methyl groups at ring carbon increases the hydrolysis rate by a factor of 10 in each step, indicating cation formation in the transition state as in acetal hydrolysis. Equilibrium protonation before hydrolysis becomes evident from an increasing rate of hydrolysis with a decreasing pH value (Table 3). Below pH 3 no further increase of rate is observed, so that protonation is assumed to be complete. 

Next the xylene was distilled away, the liquid residue dissolved in about 80 ml carbon tetrachloride and the hydrochloride precipitated through introduction of hydrochloric acid gas. The hydrochloride was dissolved in about 100 ml acetone and the solvent subsequently distilled away, whereby excess hydrochloric acid passed over with it. This operation was repeated until no excess acid was present. 

An important task remaining is the stereocontrolled introduction of a methyl group at C-8. When a cold (-78 °C) solution of 14 in THF is treated successively with LDA and methyl iodide and then warmed to -45 °C, intermediate 24 admixed with minor amounts of the C-8 epimer is formed in a yield of 95 %. The action of LDA on 14 generates a lactone enolate which is alkylated on carbon in a diastereoselective fashion with methyl iodide to give 24. It is of no consequence that 24 is contaminated with small amounts of the unwanted C-8 epimer because hydrolysis of the mixture with lithium hydroxide affords, after Jones oxidation of the secondary alcohol, a single keto acid (13) in an overall yield of 80%. Apparently, the undesired diastereoisomer is epimerized to the desired one under the basic conditions of the saponification step. 

Recently, Oldfield Ellis (1991) have examined the reinforcement of glass-ionomer cement with alumina (Safil) and carbon fibres. The introduction of only small amounts of carbon fibres (5% to 7-5% by volume) into cements based on MP4 and G-338 glasses was found to increase considerably both the elastic modulus and flexural strength. There was an increase in work of fracture attributable to fibre pull-out. A modulus as high as 12-5 GPa has been attained with the addition of 12% by voliune of fibre into MP4 glass (Bailey et al, 1991). Results using alumina fibre were less promising as there was no fibre pull-out because of the brittle nature of alumina fibres which fractured under load. 

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