Yields, by alkylation

Which of the alkynes of molecular formula CsHs can be prepared in good yield by alkylation or dialkylation of acetylene Explain why the preparation of the other CsHg isomers would not be practical. 

Alkenyllithium reagents can be alkylated in good yields by alkyl iodides and bromides.79... 

The described method of dialkylation of anilines is essentially that of Billman and co-workers. It has not previously been applied to m-trifiuoromethylaniline. m-Trifluoromethyl-N,N-dimethylaniline has been prepared in 29% yield by alkylating m-trifluoromethylaniline with methyl iodide. ... 

Both types of thiatriazoline mentioned above and 4,5-dialkyliminothiatriazolines may be prepared in moderate to high yield by alkylation of 5-alkylamino-, 5-arylamino- and 5-sulfonylamino-thiatriazoles with trialkyloxonium tetrafluoroborates (equation 48). Thiatriazolines are formed exclusively with this reagent (78JCS(P1)1440). The thiatriazoline tetrafluoroborates are crystalline solids which may be stored at room temperature and serve as convenient sources for the thermally labile free bases (75). These may be liberated with aqueous NaHC03 (78JCS(P1)1440). 

Dibenzyl ditellurium was obtained in 70% yield by alkylation of the electrochemically generated ditelluride dianion with benzyl chloride in acetonitrile3. The ultrasonically promoted electrochemical reduction of tellurium powder was performed in H-type cells with the compartments separated by glass frits. Acetonitrile served as solvent and tetrabutylammonium tetrafluoroborate or hexafluorophosphate as the supporting electrolyte. At potentials beyond -1.1 V the dark-red ditelluride dianion is formed in the cathode and in the central compartment3. 

Salts of sulfinic acids ace converted to sulfones by the action of pri-lary/ secondary, and benzyl halides, alkyl sulfates, and aryl halides in which the halogen atoms are activated by nitro groups in the ortbo or para positions. The reaction fails with t-amyl halide. The yields vary widely, depending upon the nature of the reactants. From salts of benzenesulfinic acid and simple alkylating agents, sulfones are produced in 50-90% yields. Satisfactory results have been obtained when the aryl sulfinic acid contains nitro, cyano, and acetamido groups. Keto sulfones are made in 48-62% yields by alkylation with a-halo ketones. ... 

Esterification of hindered carboxylic acids. Hindered carboxylic acids can be estcrified in high yield by alkylation of their potassium salts in ethanol-HMPT. In a typical procedure an acid such as (1) is dissolved in 50% cthanol-HMPT powdered potassium hydroxide is added and the mixture is heated at 50° until solution is complete. 

The thioalkyl-containing macrobicyclic complexes have been dealkylated and realkylated easily under the action of potassium thiolates in aprotonic media (Scheme 14). The products of de- and realkylation reactions were detected by PD and FAB mass spectrometry. In this respect the thioalkyl-containing clathrochelates are close to the aryl alkyl sulfides. In the course of thioalkyl derivative synthesis with an excess of potassium thiolate, a mixture of dealkylated products was obtained in addition to the desired hexathioalkyl clathrochelates. The addition of corresponding alkyl iodide and potassium carbonate to the reaction mixture in the final stage of reaction led to an increase in yields by alkylation of HS groups, resulting in the side dealkylation process [65]. 

Substituted thiolactams (65) are obtained from lactams (63) in SS-100% yield by alkylation with Meerwein reagent and subsequent thiolysis of the resulting imidium salt (64 equation 29). The ap-proach has been extended to other thiolactams and acyclic examples employing a cyanohydrin derivative (66 equation 30). Similarly, A, N-acetals of formyl cyanide, (R2N)2CHC N, yield thioformamides on treatment with HaS. ... 

The salt is prepared in 62% yield by alkylation of di-r-butylcarbodiimide with trimethyloxonium tetrafluoroborate. ... 

Etherification. Ethers can be prepared in good yield by alkylation of thallium (1) aDcoxides in acetonitrile (equation 1). The reaction has been used to date... 

Quaternization of the nitrogen atom in a heterocyclic system can activate the ring towards addition reactions. An oxazoline moiety was converted to an aldehyde in 97% overall yield by alkylation of oxazoline with MeOTf, reduction with sodium boro-hydride, and hydrolysis of the resulting aminal (eq 10). Alternatively, treatment of an TV-methylated oxazolium triflate with a Grignard reagent followed by aqueous acid produced a ketone. Reaction of alkenyl oxazoles with MeOTf induced spontaneous intramolecular [4 -i- 2] cycloaddition at room temperature leading to a hydroindole or a hydroisoquinoline after reduction by sodium borohydride (eq 11). ... 

A number of new routes to a-methylene esters (121) have been developed (see also ref. 110). Perhaps the simplest involves the treatment of malonic acid half-esters with formaldehyde in pyridine containing piperidine. Yields are ca. 80%. A somewhat less efficient scheme utilizes a reaction between silyl keten acetals and chloromethyl methyl ether followed by pyrolytic removal of methanol (160 °C, KHS04). Esters (121) can also be obtained in 31—83% yield by alkylation of the Diels-Alder adduct of dimethylfulvene and methyl acrylate followed by a retro-Diels-Alder reaction. " ... 

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