C4-alkylations

One further word about naming alkyl groups the prefixes sec- (for secondary) and tert- (for tertiary) used for the C4 alkyl groups in Figure 3.3 refer to the number of other carbon atoms attached to the branching carbon atom. There are four possibilities primary (1°), secondary (2°), tertiary (3°), and quaternary (4°). 

Tossing, F.P. Semeluk, G.P. Free Radicals by Mass Spectrometry. XLII. Ionization Potentials and Ionic Heats of Formation for C1-C4 Alkyl Radicals. Can. J. Chem. 1970, 48, 955-965. 

N. (2008) Continuous supercritical iC4/ C4= alkylation over H-Beta and H-USY Influence of the zeolite strudure. Appl. Catal A, 336, 51-71. 

R = H, (CH2)2NH2, C1-C4 alkyl and cycloalkyl groups, CH2OCH3 R2 = Ph, 2-thienyl, 3-(C6H50)CeH4... 

PBs incorporating C3 and C4 alkyl bridges have been shown to readily form intramolecular P-B interactions, leading to unstrained five- and six-membered rings (Figure 9). The monomeric closed structures of 41a, 41d, and 42a were supported by diagnostic 31P and rlB NMR chemical shifts in solution, and short P-B distances (2.02-2.10 A) in the solid state.53,57... 

Scheme 11. The osmium(l l)-promoted C4 alkylation of phenol with MVK.

Regiocontrol Although Michael additions to [Os]-phenol occur selectively at C4, addition at C2 is thermodynamically favored for phenol complexes that are substituted at C4. For C4-substituted phenol complexes, the regiochemistry can be controlled by varying the time, temperature, and catalyst (Figure 6) [29]. Additions of MVK to the estradiol complex 90 and the p-cresol 94 at —40 °C in the presence of an amine base catalyst result in regioselective C4 alkylation in high yields (91 and 95). However, when this reaction is performed at room temperature in the presence of a Zn2+ co-catalyst, the Michael acceptor adds at C2 to afford... 

There are two categories of C2—C4 alkyl radical decomposition complexes (i) H split-off, and (ii) alkyl split-off. The first of the two complexes is the looser The activation energy for methyl or ethyl radical... 

Phthalidylnitromethane (9) and its alkyl- and dialkyl-substituted derivatives (R = H, Me R = H, C, -C4 alkyl) were hydrogenated to the corresponding amino compounds... 

Isobutane efficiency will increase (less iC4 required for C4 alkylation than C3 alkylation). 

Cooper et al. (1992, 1997) identified a homologous series of C1-C4 alkyl phosphonic acids and alkanesulfonic acids in water extracts from Murchison. Isomeric diversity was apparent with five of the eight possible C1-C4 alkyl phosphonic and seven of the eight C1-C4 alkanesulfonic acids identified. The relative abundances of both classes of compound decreased exponentially with increasing carbon number. 

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