Addition of Alkyl Groups

Luche reported that when a zinc-copper couple was used, alkyl halides reacted with conjugated carbonyl compounds and nitriles to give 

4-addition products in good yields under sonication conditions (Eq. 10.26).  

Similar additions also occurred on vinylphosphine oxides. When the optically active vinylphosphine oxide was used, P-chiral alkylphosphine oxide was obtained with retention of the configuration (Eq. 10.27)  

The diastereoselective ultrasonically induced zinc-copper 1,4-addition of alkyl iodides to chiral a, P-unsaturated systems in aqueous media was studied by Suares and co-workers the Z-isomer gives good diastereos-electivities while reactions with the E-isomer are nonstereoselective. The 1,4-addition to chiral y, a-dioxolanyl-a, P-unsaturated esters also proceeds with good yields (51-99%) (Eq. 10.29).  

Li and co-workers reported the conjugate addition of an alkyl group 

Giese and coworkers studied the diastereoselectivity associated with a related addition in water (Eq. 4.71) and foimd that the anti-isomer was the major product if the attacking radical is bulky. The results were explained that the more stable A-strain conformer of the alkene reacts slower with bulky alkyl radical than the less stable FeUdn-Anh conformer. 

Li and coworkers reported the conjugate addition of alkyl groups to enamides mediated by zinc in aq. NH4CI to generate a -amino acid derivatives (Eq. 4.73). No reaction was observed in the absence of water. Both secondary and tertiary alkyl groups such as linear (2-butyl, 2-propyl, 2-pentyl), cyclic (cyclohexyl, cyclopentyl, cycloheptyl), and bulky ones (tert-butyl) were all transferred to the substrate successfully. Even simple primary iodides and methyl iodide provided the desired products in good yields. Miyabe et al. as well as Jang and Cho reported the addition of alkyl radicals from alkyl iodide to a,p unsaturated ketones, esters, and nitriles mediated by indium in aqueous media. Indium-mediated Michael addition of allyl bromide to l,l-dicyano-2-arylethenes also proceeded well in aqueous medium.  

Miyaura and coworkers reported the Rh(l)-catalyzed conjugate addition of aryl- or 1-alkenylboronic acids, RB(OH)2,to enones in high yields at 50°C in an aqueous solvent. A 

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Conjugate Addition of Alkyl Groups Organocopper Reactions... 

The stereospecific base-cleavage of the trimethylsilyl group in 1,3-dithiane 1-oxides 499 enables to obtain the specifically deuteriated products 500 (equation 303), A nitro group in y-nitroalkyl sulphoxides 501 (obtained by the Michael addition of nitroalkanes to a, j8-unsaturated sulphoxides) is replaced by hydrogen by means of tributyltin hydride (equation 304). This reagent does not affect the sulphinyl function. The overall procedure provides an efficient method for the conjugate addition of alkyl groups to a, -unsaturated sulphoxides . ... 

Michael acceptors and 1,4-addition of alkyl group is a normal process. The reaction mechanism is not clear, but the process via addition of alkyl radicals and subsequent elimination of N02 radical is one of the possible routes. Recently, several related reactions have been reported, as shown in Eq. 4.7698, Eq. 4.77," and Eq. 4.78,100 in which alkyl radicals are involved. The reaction of trialky lgallium compounds with nitrostyrene gives also a similar substitution product (Eq. 4.79).101... 

In general, C-acyl nitroso compounds-9,10-dimethylanthracene cycloadducts derived from hydroxamic acids (-R = alkyl, aryl, ti/2 = 4.1 h for -R = -Ph at 60°C) decompose more slowly than those derived from N-hydroxycarbamates or N-hydroxyureas [11, 13, 14]. Further addition of alkyl groups to the N atom of N-hydroxyurea-derived cycloadducts produces a further increase in the rate of the retro-Diels-Alder reaction of these cycloadducts [36]. These general trends suggest the possibility of the development of acyl nitroso compound-9, 10-dimethylanthracene cycloadducts as a general class of HNO or NO donors with varied release profiles. 

Bennett and Larter (1997) also studied the solvation of alkylphenols in crude oil-water systems at equilibrium to obtain partitioning coefficients under variable temperature, pressure, and water salinity concentration. Alkylphenol depletion from crude oil, expressed by phenol, cresols, and 3,5 dimethyl phenol, versus temperature in a range of 25-125°C, is given in terms of partition coefficient (P) values (Fig. 16.22). Partition coefficient values increase with addition of alkyl groups to the phenol nucleus. Note that the alkylphenol partition coefficient curves for different isomers tend to converge at higher temperatures and, as a consequence, differences between phenol and p-cresol decrease with increases in temperature. Similar results for oil-deionised water and oil-brine experiments show that increasing temperature leads to a decrease in partition coefficient values. 

The acid-catalyzed reaction of aromatics with monoolefins results exclusively in addition of alkyl groups to the aromatic ring. In contrast, the base-catalyzed reaction of aromatics with monoolefins results in alkylation... 

Propargyl alcohols By addition of alkyl groups to acetylenic carbonyl compounds (R)-( + )-/-Butyl p-tolylsulfinylacetate, 59... 

These reagents are useful in the 1,4-addition of alkyl groups to a,(l-unsaturated carbonyl systems and can also be reacted with alkyl halides to produce larger alkanes (Following fig.). The mechanism is considered to be radical based. 

Figure 1 Structures of some metal salen complexes (a) epoxidation catalysts, (b) proposed structure in the asymmetric addition of alkyl groups to alpha ketoesters with a bifunctional catalyst, and (c) oligomeric bifunctional salen catalyst for the hydrolytic catalytic resolution... 

Figure 22 Asymmetric addition of alkyl groups to aldehydes employing (MBP)Ti(OR )2 catalysts...

Table 6 MBP-H2 ligands used in the asymmetric addition of alkyl groups to aldehydes (Figure 22)...

The copper-mediated 1,4-addition of alkyl groups to a,P-unsaturated ketones affords regiochemically pure enolate anions (see also Section 7.5) which may be trapped at oxygen with silyl halides, acyl halides, or dialkylcarbonates to provide silyl enol ethers, enol acetates, or enol carbonates, respectively. These can be unmasked at a later stage by reaction with MeLi to regenerate the enolate for further elaboration. ... 

Cross-couplings. Conjugate addition of alkyl groups fiom RI to electron-deficient alkenes is promoted by a catalytic amount of NijB and borohydride exchange resin in methanol (39 examples, 40-93%). Another coupling involves alkenes and a-bromalkanoic esters. ... 

A variety of bis(sulfonamide) complexes of the form TiX2(C6H10(NSO2R)2),857-861 TiX2(PhCH(NS02R))2, and Ti((PhCH(NS02R)2))2862 have been prepared. A number of these complexes have been structurally characterized. In addition, these and related compounds have been used as catalysts for enantioselective addition of alkyl groups to aldehydes. 

The formation of TiMe(OPr )3 is spectroscopically observed in the reaction of Ti(OPr )4 with ZnMe2 in C6D6. This species has been used as a catalyst for the addition of alkyl groups to aldehydes.1 Sequential treatment of TiCU(l,2-DME) with LiMe followed by CF3CH2OH gives TiCl2Me(OCH2CF3).13... 

Alkylation and Dealkylation Reactions. Alkylalioit is the addition of alkyl group to an organic compound. This type of reaction is commonly c tied out in the presence of the Friedel-Crafts catalysts. AlCb along wit trace of HCl. One such reaction is... 

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