Aryls monoaryls

Organophosphorus compounds. Phosphorus-carbon bond fonnation takes place by the reaction of various phosphorus compounds containing a P—H bond with halides or tritlates. Alkylaryl- or alkenylalkylphosphinates are prepared from alkylphosphinate[638]. The optically active isopropyl alkenyl-methylphosphinate 778 is prepared from isopropyl methylphosphinate with retention[639]. The monoaryl and symmetrical and asymmetric diarylphosphi-nates 780, 781, and 782 are prepared by the reaction of the unstable methyl phosphinate 779 with different amounts of aryl iodides. Tnmethyl orthoformate is added to stabilize the methyl phosphinate[640]. 

An interesting observation in the solvolysis of all arylvinyl systems is the effect of added /3-aryl groups. All triarylvinyl substrates react more slowly than do the corresponding monoaryl or diaryl systems. For example, triphenylvinyl fluorosulfonate, 153, Ri =C6Hs, R = F, reacts about 2.5 times more slowly (140) in acetic acid than does a-phenylstyryl fluorosulfonate, 153, Rj = H, R = F. Similarly, trianisylvinyl bromide reacts 2.8 times and 1.2 times more slowly in 80% EtOH and in AcOH, respectively (144), than does cis-1,2-dianisylvinyl bromide. This difference probably results from increased hindrance to solvation and increased unfavorable steric interactions. 

Finally, NHC complexes of copper, formed in situ from the hnidazolium salt and CuBr have been used in the monoarylation of aniline [167]. Trinuclear Cu(I) catalysts have been applied to the arylation of pyrazoles, triazoles, amides and phenols [168] (Scheme 6.50). 

In a recent article by Botella and Najera, controlled mono- and double-Heck arylations in water catalyzed by an oxime-derived palladacycle were described [22], When the reaction was carried out under microwave irradiation at 120 °C in the presence of dicyclohexylmethylamine with only 0.01 mol% of palladium catalyst (palladium acetate or palladacycle), monoarylation took place in only 10 min with a very high turnover frequency (TOF) of > 40000 (Scheme 6.3). As regards diarylation, 1 mol% of the palladacycle catalyst and 2 equivalents of iodobenzene had to be utilized to obtain moderate to good yields of diarylated product. Whereas microwave heating at 120 °C provided a 31% yield after 10 min, a 66% isolated yield of product was obtained by heating the reaction mixture under reflux for 13 h at 100 °C. Here, the... 

The arylation of phenols also proceeds smoothly. Even the sterically overcrowded 3,5-di- r/-butylphcnol 17 reacts with 2,4,6-trimethoxyphenyllead triacetate 18 to furnish compound 19, which is isolated in 87% yield, together with 10% of the monoarylation product (Equation (6)). 

The monoaryl Cl2BiC6H2-2,4,6-Ph3 is dimeric in the solid state with Bi-Cl distances of 3.074(1) A (bridging) and 2.532(1) A (terminal).135 The Bi-C bond length (2.266(4) A) is somewhat shorter than that found in the bis and tris aryls, probably as a result of the reduced steric crowding. The intermolecular Bi-Bi distance, 4.316(1) A, is shorter than the sum of the van der Waals radii, 4.68 A. Also, this molecule displays a Menshutkin interaction138 in which there is relatively close contact between bismuth and one of the pendant aryl groups resulting in a Bi-centroid distance of 3.53 A (calculated 4.04 A). 

Despite the fact that ortho-substituted aryl halides coupled well, a double sulf-oximination of 59 with an excess of 9 to give bissulfoximine 60 was impossible under the conditions mentioned above (Scheme 2.1.1.18). Instead, monoarylated product 61 was obtained in good yield (75%) [45b]. 

With few exceptions the dianions of monoalkyl and monoaryl phosphates are unreactive but with a good leaving group, e.g. carboxylate, dianions undergo hydrolysis. The same reasoning applies to a dinitrophenoxide anion and the pH-rate profile for the hydrolyses of 2,4- and 2,6-dinitrophenyl phosphates differs from those of other aryl phosphates in that the dianion is more reactive than the monoanion species (Fig. 2)22-23. This reactivity is at-... 

Monoarylation of diamines has been achieved by treatment of excess diamine with an arylating reagent (Scheme 10.19) [82-84]. If the arylation is slow the statistically expected amounts of mono- and diarylated product will usually result. An effective means removing excess diamine will, however, be required the purification of the products. 

A new type of triaryl phosphine-functionalized imidazolium salt containing cations such as (6) has been prepared. Palladium complexes of (6) generated in situ have been used successfully in Heck-type reactions of aryl halides with acrylates and of 4-bromotoluene with styrene derivatives.34 The first Heck-type reaction of aryl halides with allenes has been reported. 1,3-Double arylations were observed with 3-substituted-l,2-allenyl sulfones, while 1-monoarylation was favoured with 3,3-disubstituted-l,2-allenyl sulfones.35 It has been shown that the a-arylation of methane-sulfonamides (7) may be achieved using palladium catalysis reaction proceeds through the sulfonamide enolates.36 It is also reported that palladium cross-coupling of alkynes with /V - (3 - i odophe n y I an i I i ncs) may lead to the formation of substituted carbazoles.37... 

Arylcycloalkenes.10 These products can be obtained by Pd-catalyzed coupling of aryl iodides and cycloalkenes (5 equiv.) in DMF containing tetrabutylammo-nium chloride and KOAc (2 equiv.) Other acetate bases are less effective. A large excess of the cycloalkene is required to effect monoarylation. 

The monoarylated enamine can then be acylated to form a mixture of 2-acyl-2-arylcyclohexanone and 2-aryl-6-acylcyclohexanone. This was held to indicate that arylation affords two enamines, 62 and 63, which differ only in the position of the double bond. The reaction involving acyl halides could be explained under the assumption that in the more probable enamine structure (with conjugation through the free electron pair on nitrogen, the double bond, and the aromatic ring) it is the hydrogen atom on C(6) which is more acidic. 

N-Arylpiperazines are common substructures of molecules that influence various biological processes and, therefore, the arylation of monoprotected and the single arylation of unprotected piperazines has been studied. As discussed above, the monoarylation of piperazines... 

Electrophilic substitution into the aryl nucleus of a 2,5-diaryl-l,3,4-oxadiazole can be carried out but such reactions are difficult with the more acid sensitive monoaryl-1,3,4-oxadiazoles. A variety of transformations of the functional group on an aryl ring in a mono-or di-aryl-1,3,4-oxadiazole have been performed (66AHC(7)183). 

The reaction of 4-(methoxycarbonyl)chroman-3-one with aryllead triacetates afforded the expected 4-aryl derivatives 28 in moderate to good yields (see Section 9.09.2.1, Equation (6)). However, with longer reaction times the products of bis-arylation 29 were obtained in moderate yields (Equation (35)). Unsymmetrically disubstituted chro-man-3-ones were obtained by treatment of the pure product of monoarylation, the 4-monosubstituted compound, with a second aryllead triacetate (Equation (36)). 

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