Ar/Alkyl couplings

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaHy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphoms [7723-14-0] produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-Hthiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has Httie commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

Haloalkynes (R—C=C—X) react with ArSnBu3 and Cul to give R—C= C—Ar. Acetylene reacts with two equivalents of iodobenzene, in the presence of a palladium catalyst and Cul, to give 1,2-diphenylethyne. 1-Trialkylsilyl alkynes react with 1-haloalkynes, in the presence of a CuCl catalyst, to give diynes and with aryl triflates to give 1-aryl alkynes. Alkynes couple with alkyl halides in the presence of Sml2/Sm. Alkynes react with hypervalent iodine compounds " and with reactive alkanes such as adamantane in the presence of AIBN. ... 

In a reaction similar to 12-50, azoxy compounds can be prepared by the condensation of a nitroso compound with a hydroxylamine. The position of the oxygen in the final product is determined by the nature of the R groups, not by which R groups came from which starting compound. Both R and R can be alkyl or aryl, but when two different aryl groups are involved, mixtures of azoxy compounds (ArNONAr, ArNONAr, and Ar NONAr ) are obtained and the unsymmetrical product (ArNONAr ) is likely to be formed in the smallest amount. This behavior is probably caused by an equilibration between the starting compounds prior to the actual reaction (ArNO -I- Ar NHOH Ar NO - - ArNHOH). The mechanism has been investigated in the presence of base. Under these conditions both reactants are converted to radical anions, which couple ... 

Unsymmetrical coupling of vinylic, alkynyl, and arylmercury compounds was achieved in moderate-to-good yields by treatment with alkyl and vinylic dialkylcopper reagents (e.g., PhCH=CHHgCl -t- Mc2CuLi PhCH=CHMe). Unsymmetrical biaryls were prepared by treating a cyanocuprate ArCu(CN)Li (prepared from ArLi and CuCN) with an aryllithium Ar Li. ... 

Piperazine, N-alkylation with benzyl chloride, 42,19 Piperazine, 1-benzyl-, 42,19 Piperidine, addition to ethylene, 43, 45 as catalyst for Claisen-Schmidt condensation, 41,40 Piperidine, 1-ethyl-, 43, 45 Piperidine, 1-(2-naphthyl)-, 40,74 Pivalic add, oxidative coupling to a,ar a, a -tetramethyladipic add, 40, 92... 

The behavior of BnMgBr (5d) is similar to that observed for compounds with higher alkyl groups, i.e. only the coupling product was detected and the earlier report on the additional formation of benzyl alcohol was not confirmed. On the other hand, reactions of Ar" radicals formed in the anodic oxidation of aryl Grignard reagents are different from those established for Aik, as is evident from the percent distribution of parent radicals in major products given in Table 7. 

A second side reaction suffered by Ar(4)-unfunctionalized quinoxali-nones leading to racemization at the a-carbon was revealed in the closely related studies of Morales and co-workers, who assembled the [6,6] ring system from 4-fluoro-3-nitrobenzoic acid coupled as an ester to Wang resin (lb) (Scheme 12).9 This undesirable side reaction could also be prevented by functionalization of iV(4) prior to cleavage, which in this instance was accomplished by acylation with chloroformates and thiochloroformates. Derivatization at (V(l) was again effected using the Ellman alkylation protocol and provided optically pure samples of the quinoxalinones (72). 

Although the heteroaryl Heck reactions of chloropyrazines with pyrrole itself were low-yielding for both mono- and bis-arylation products, better yields were obtained for N-phenylsulfonylpyrrole. Bulkier alkyl substituents on the pyrazine ring promoted the formation of C(3)-substituted pyrroles. The C(3)-substituted pyrrole 64 was the major product (62%) for the coupling of 1 and Ar-phenylsulfonylpyrrole, while C(2)-subslituted pyrrole 63 was a minor product (15%). 

---