Butanes aryl-substituted—

One of the very few examples of the use of non-aryl substituted 1,2-diketones in Hinsberg syntheses involved activation of the sulfur component with nitriles, rather than esters (Scheme 44). Thus, the reaction of butane-2,3-dione with 2,2 -thiobis (acetonitrile) led to mononitrile-monoamide 27 [73],... 

The central bond of the l-(arylsulfonyl)bicyclo[1.1.0]butane system behaves like the double bond of a, /i-unsaturated sulfones to give alkyl-substituted cyclobutyl aryl sulfones on treatment with organometallic reagents (equation 20)17. This method has been applied... 

As mentioned in Sections 3.1.6 and 4.1.3, cyclopropenes can also be suitable starting materials for the generation of carbene complexes. Cyclopropenone di-methylacetal [678] and 3-alkyl- or 3-aryl-disubstituted cyclopropenes [679] have been shown to react, upon catalysis by Ni(COD)2, with acceptor-substituted olefins to yield the products of formal, non-concerted vinylcarbene [2-1-1] cycloaddition (Table 3.6). It has been proposed that nucleophilic nickel carbene complexes are formed as intermediates. Similarly, bicyclo[1.1.0]butane also reacts with Ni(COD)2 to yield a nucleophilic homoallylcarbene nickel complex [680]. This intermediate is capable of cyclopropanating electron-poor alkenes (Table 3.6). 

Cyclocarbonylation of o-iodophenols 503 with isocyanates or carbodiimides and carbon monoxide in the presence of a catalytic amount of a palladium catalyst (tris(dibenzylideneacetone)dipalladium(O) Pd2(DBA)3) and l,4-bis(di-phenylphosphino)butane (dppb) resulted in formation of l,3-benzoxazine-2,4-diones 504 or 2-imino-l,3-benzoxazin-4-ones 505 (Scheme 94). The product yields were dependent on the nature of the substrate, the catalyst, the solvent, the base, and the phosphine ligand. The reactions of o-iodophenols with unsymmetrical carbodiimides bearing an alkyl and an aryl substituent afforded 2-alkylimino-3-aryl-l,3-benzoxazin-4-ones 505 in a completely regioselective manner <1999JOC9194>. On the palladium-catalyzed cyclocarbonylation of o-iodoanilines with acyl chlorides and carbon monoxide, 2-substituted-4f/-3,l-benzoxazin-4-ones were obtained <19990L1619>. 

Tertiare Nitro-aliphaten, mit einer desaktivierten Aryl-Gruppe in a-Stellung lassen sich mit 2-Lithio-2-nitro-propan bzw. -butan in Phosphorsaure-tris-[dimethylamid], DMF oder DMSO durch nukleophile Substitution unter C—C-Knupfung zu 2-Aryl-l -nitro-... 

It appears that mass spectrometry is of considerable value in structure determination although, at present, it is not possible to differentiate between 2- and 4-substituted isomers. The technique has been used to establish the structure of 4-(imidazol-4-yl)butane-1,2,3-triol55 which, unlike most carbohydrate derivatives, shows a molecular ion. The mass spectra of 2-alkylbenzimidazoles246 and mercaptoimidazoles124 have been examined, while use has been made of mass spectrometry in the identification of some alkyl, aryl, and acyl imidazoles.138... 

However, the potential range within which the spin trap is electro-inactive is considerably reduced. This, the commonly used trap nitroso-t.-butane is reduced at a potential -0.98 V (vs. Ag/AgI) at mercury in dimethyl-formamide. The range may be extended by substitution of appropriate aryl groups for butane [114]. Nitroso compounds also present a problem in that some compounds have been shown to undergo a monomer/dimer equilibrium in solution in which only the monomeric form acts as a radical trap. Hence, for nitroso compounds, it is necessary to understand this equilibrium, as well as the electrochemical properties of the trap, before it may be used in the investigation of electrode reactions. 

Finke, P.E. etal. (2001) Antagonists of the human CCR5 receptor as anti-HIV-1 agents. Part 2 structure-activity relationships for substituted 2-aryl-l-[N-(methyl)-N-(phenylsulfonyl)amino]-4-(piperidin-l-yl)butanes. Bioorganic C Medicinal Chemistry Letters, 11 (2), 265-270. 

Kollar L, Farkas E, Batiu J. Synthesis of aryl-butanal isomers by hydroformylation of substituted allylbenzene and prope-nylbenzene. J. Mol. Cat. A Chem. 1997 115 283-288. 

---