Alkylation and Functionalization

Review P. Perlmutter, Conjugate Addition Reactions in Organic Synthesis. Tetrahedron Organic Chemistry Series, Vol 9, Pergamon, New York (1992) 

See also page 655, Section 4, for the synthesis of vinylic halides, and page 545, Section 9. 

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Ultraviolet photoelectron spectroscopy allows the determination of ionization potentials. For thiazole the first experimental measurement using this technique was preformed by Salmona et al. (189) who later studied various alkyl and functional derivatives in the 2-position (190,191). Substitution of an hydrogen atom by an alkyl group destabilizes the first ionization potential, the perturbation being constant for tso-propyl and heavier substituents. Introduction in the 2-position of an amino group strongly destabilizes the first band and only slightly the second. 

Transesterification of methyl methacrylate with the appropriate alcohol is often the preferred method of preparing higher alkyl and functional methacrylates. The reaction is driven to completion by the use of excess methyl methacrylate and by removal of the methyl methacrylate—methanol a2eotrope. A variety of catalysts have been used, including acids and bases and transition-metal compounds such as dialkjitin oxides (57), titanium(IV) alkoxides (58), and zirconium acetoacetate (59). The use of the transition-metal catalysts allows reaction under nearly neutral conditions and is therefore more tolerant of sensitive functionality in the ester alcohol moiety. In addition, transition-metal catalysts often exhibit higher selectivities than acidic catalysts, particularly with respect to by-product ether formation. 

This reaction, cataly2ed by uv radiation, peroxides, and some metal catalysts, eg, platinum, led to the production of a broad range of alkyl and functional alkyl trihalosilanes. These alkylsilanes have important commercial value as monomers and are also used in the production of sihcon fluids and resins. Additional information on the chemistry of sihcon hahdes is available (19,21—24). 

Huonnaled Organometallics Perfluoto-alkyl and Functionalized Pertiuoroalfcyl OrganomeuUic Reagents in Oigaruc Synthesis Burton, D J, Yang, Z Y Tetrahedron 48, 189-275 297... 

Since l-heterobut-l-en-3-ynes are readily alkylated and functionalized at the terminal acetylenic carbon atom, their reaction with hydrazines makes it possible to introduce diverse (including functional) substituents into the pyrazole ring. For instance, from benzylated methoxybutenyne 112, isomeric 2-phenylethylpyrazoles 113 were obtained in 74% yield (81H146). 

The chemistry of silicone halides was recently reviewed by Collins.13 The primary use for SiCU is in the manufacturing of fumed silica, but it is also used in the manufacture of polycrystalline silicon for the semiconductor industry. It is also commonly used in the synthesis of silicate esters. T richlorosilane (another important product of the reaction of silicon or silicon alloys with chlorine) is primarily used in the manufacture of semiconductor-grade silicon, and in the synthesis of organotrichlorosilane by the hydrosilylation reactions. The silicon halohydrides are particularly useful intermediate chemicals because of their ability to add to alkenes, allowing the production of a broad range of alkyl- and functional alkyltrihalosilanes. These alkylsilanes have important commercial value as monomers, and are also used in the production of silicon fluids and resins. On the other hand, trichlorosilane is a basic precursor to the synthesis of functional silsesquioxanes and other highly branched siloxane structures. 

Deady and Zoltewicz studied the influence of a larger set of substituents on the kinetics of quaternization of derivatives 20 and 21 including alkyl and functional groups R in position-2 and/or R-6 (72JOC603) (Scheme 15). As expected, the kinetic results are poorly correlated with pK values. Separate correlation lines were required for 2-substituted and 2,6-disubstituted pyridines. It was suggested that steric effects are superimposed on electronic effects, and that steric effects are nearly constant for ortho substituents like NH2, Me, Cl, Br, and CN, but are more important for Et, CH2Ph, 2-pyridyl, and C02Me. 

A series of A -substituted D-araiwo-piperidinol phosphates, e.g. 253, were prepared from the 1,2,3-inositol triphosphate 251, by periodate cleavage yielding 252, which was converted to 253 by aminolysis and NaBH4 reduction. A wide range of alkyl and functionalized R groups were used. ... 

Foster LJR, Lenz RW, Fuller RC (1999) Intracellular depolymerase activity in isolated inclusion bodies containing polyhydroxyalkanoates with long chain alkyl and functional substituents in the side chain. Int J Biol Macromol 26 187-192... 

Denmark has described several chiral bis-phosphoramides as Lewis base activators of weak Lewis acid SiCL and demonstrated their ability to mediate an enantioselective Passerini-type reaction. Catalytic bis-phosphoramide 36 and stoichiometric SiCU, in the presence of a proton scavenger (Htinig s base), promoted the formation of a-hydroxyamides with remarkably good enantioselectivity and yield. A variety of aromatic and unsaturated aldehydes and aryl, alkyl, and functionalized alkyl isocyanides proved to be useful and effective starting materials. High yields of Passerini products were attributed to the production of imidoyl chloride 37, which reduced the prevalence of the nitrilium intermediate and prevented the addition of a second equivalent of isonitrile. 

IR spectra contain a wealth of information about the structures of compounds. We show some of the information that can be gathered from the spectra of octane and methylbenzene (commonly called toluene) in Figs. 2.11 and 2.12. In this section we shall learn how to recognize the presence of characteristic IR absorption peaks that result from vibrations of alkyl and functional groups. The data given in Table 2.7 will provide us with key information to use when correlating actual spectra with IR absorption frequencies that are typical for various groups. 

A detailed study of n.m.r. spectra has provided extensive data on chemical shifts and coupling constants in respect of a series of monophenyl-thiazoles, and their derivatives bearing alkyl and functional substituents in their hetero-rings. The chemical shifts were correlated with the net from electron density and energy diagrams, and the overall results were compared with those previously obtained in respect of thiazole and its methyl derivatives. 

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