SYNTHESIS OF BI ARYLS

Scheme 6.30 Domino Sonogashira sequence for the synthesis of bis(aryl)-alkynes.

To date, the organometallic chemistry of copper, in terms of isolation and structural characterization of compounds, is essentially limited to the Cu(I) oxidation state. Only a very few examples of other oxidation states are known. The older literature offers a reported synthetic procedure for the synthesis of bis(aryl)copper(II) compounds [33, 34] (see Scheme 1.2), but this result has never been reproduced by others. 

The mechanism proposed for the acid-catalysed synthesis of bis(aryl)-alkanes [394] [scheme (E)] follows the main features of the aldolisation scheme (H). The protonised form of the carbonyl compound reacts by an electrophilic attack with the quinonoid structure of the aromatic molecule (e.g. phenol), viz. 

Although the sulfone activated biphenyl and the ketone activated naphthalene moiety for the displacement polymerization have been reported by Attwood et al. [11], these were rediscovered by Cummings et al. [12] and Hergenrother et al. [13], respectively, for the synthesis of poly(aryl ethers). Recently, Singh and Hay [14] reported polymers containing 0-dibenzoyl benzene (1,2,3) moiety by reaction between bis(O-fluorobenzoyl) benzene or substituted benzene with bisphenates of alkali metal salt in DMAC as follows ... 

Recently, the pyrazole group containing bisphenols have been synthesized from activated aromatic dihalides and 3,5-bis (4-hydroxy phenyl)-4-phenyl pyrazole or 3,5-bis(4-hydroxy phenyl)-1,4-diphenyl pyrazole. A novel synthesis of imido aryl containing bisphenols has been reported [32]. N-substituted l,4-bis(4-hydroxy phenyl)-2,3-naphthalimides were prepared from phenolphthalein and copolymerized with aromatic sulfone or ketone difluorides to obtain the poly(imidoaryl ether) sulfones/ ketones. 

The palladium-catalyzed asymmetric hydrosilylation of styrenes has been applied to the catalytic asymmetric synthesis of l-aryl-l,2-diols from arylacetylenes (Scheme 6).46 Thus, ( )-l-aryl-2-(trichlorosilyl)ethenes, which are readily generated by platinum-catalyzed hydrosilylation of arylacetylenes, were treated with trichlorosilane and the palladium catalyst coordinated with MOP ligand 12f to give 1 -aryl-1,2-bis(silyl)ethanes, oxidation of which produced the enantiomerically enriched (95-98% ee) 1,2-diols. 

In comparison to the N- and S-counterparts, alkoxides possess lower nucleophilicity. Therefore, the reductive elimination process to form the C—O bond is much slower than those to form C— N and C—S bonds [103]. Palucki, Wolfe and Buchwald developed the first intramolecular Pd-catalyzed synthesis of cyclic aryl ethers from o-haloaryl-substituted alcohols [104]. For example, 3-(2-bromophenyl)-2-methyl-2-butanol (91) was converted to 2,2-dimethylchroman (92) under the agency of catalytic Pd(OAc)2 in the presence (S)-(-)-2,2 -bis(di-p-tolylphosphino)-l,r-binaphthyl (Tol-BINAP) as the ligand and K2CO3 as the base. The method worked well for the tertiary alcohols, moderately weE for cychc secondary alcohols, but not for acyclic secondary alcohols. 

Scheme 2.51 Synthesis of bis- and trisallenes by palladium-catalyzed coupling of allenylindium reagents with aryl halides.

Transformation of a phosphonio-substituted phospholide derivative under conservation of the r-electron system has been demonstrated in a number of cases which include substitution of a ring-hydrogen atom, replacement of a PRs -moiety by a hydride, or reductive de-arylation of a PhsP " - to a phosphinyl substituent PPh2. Subsequent re-quaternisation of the latter allows the formal substitution of a PhsP " - by a modified Ph2(R)P -moiety in a two-step reaction. The application of this scheme is not only perfectly suitable for the synthesis of bis-phosphonio-benzophospholides with different phosphonio-moieties but, since the last reaction stage tolerates a variety of functional groups in the electrophile, offers as well a convenient pathway for the synthesis of side-chain functionalised phosphonio-phospholide derivatives from more simple substituted precursors. 

The reaction of ethyl A-arylcarbamates 3 with l-bromo-3,3-dimethyl-2-buta-none or l-bromo-3-ethyl-3-methyl-2-pentanone 4 in the presence of lithium bis(trimethylsilyl)amide (LiHMDS) results in the one-step synthesis of 3-aryl-5-ferf-butyl-2(3/T)-oxazolones 7 in fair to good yields (Fig. 5.2 Table 5.1, Fig. 5.3). This method is efficient for the preparation of bulky 5-substimted-2(37f)-oxazo-lones. 

Following the successful synthesis of the aryl xanthate complexes, Chen and Fackler reported on the synthesis and structural characterization of the diamagnetic, monomeric bis(0-2,4,6-trimethylphenylxanthato)palladium(II) complex (117). A typical PdS4 unit was found in this complex in which the shorter S2C-0 bond length [1.330(12) A] compared to the Ph-0 bond length [ 1.439(16)] indicates a certain importance of the S2C=6 resonance form in the structure of the xanthate ligand. 

IV,N,N -Tris(trimethylsilyl)amidines have been used recently as precursors for a number of inorganic heterocycles and metallacycles,1 some of which are being studied in light of their unusual solid state properties2. Boere et al. reported the synthesis of several aryl-substituted persilylated benzamidines and the related compound /V,N,N, N",N",Ar" -hexakis(trimethylsilyl)-l,4-benezenedicarboximidamide (hereafter referred to as HBDA) 3 the present syntheses, which are generally based on the same reaction of an aryl-substituted carbonitrile with lithium bis(trimethylsilyl)amide, offer more facile routes to representative mono- and polyfunctional carboximidamides (i.e., amidines) as well as the prototypal derivative N,N,N -tris(trimethyl-silyl)formimidamide.4 As before, the crystalline diethyl ether adduct of lithium bis(trimethylsilyl)amide5 is favored over the nonsolvated amide in these syntheses the preparation of the diethyl ether adduct is also described here. 

R = alkyl, aryl)], commonly used for the synthesis of bis (p-anion)dirhodium(i) tetracarbonyls, has revealed the presence of [Rh2(CO)4XY] type intermediates containing two different bridging ligands.129... 

Chopa, A.B., Lockhart, M.T. and Silbestri, G. (2002) Synthesis of bis-(trimethylstannyl)aryl compounds via an SRN1 mechanism with the intermediacy of monosubstitution products. Organometallics, 21, 5874-5878. 

In an elegant synthesis of indole derivatives, regioselective introduction of oxygen has been achieved by first introducing iodine into the aryl system followed by displacement with methoxide (equation 27)242,243. Also, aryl polyethers have been synthesized by reaction of bis-aryl chlorides with bis-phenols (equation 28)244. 

Various electrophiles bring about the cyclisation of o-(l-alkynyl)benzoates and (Z)-2-alken-4-ynoates to isocoumarins and pyran-2-ones in high yields extension to the synthesis of bis-coumarins and hetero-fused pyranones is successful (Scheme 25) <03JOC5936>. 3-Aryl-4-iodoisocoumarins, prepared in a similar manner, undergo Stille reactions and can readily be deiodinated <03T2067>. 

A partially related reaction is the photochemical synthesis of bis(pyrrolyl)- and bis(indolyl)methanes by irradiation of (hetero)aryl aldehydes in the presence of the... 

A similar sequence with 5-substituted pyrrole boronic acids 89 affords a range of 2-aryl- and 2-hetarylpyrroles 90 [68]. Boronic acids 89 were prepared as shown for 84. This study included the synthesis of bis-pyrrole 91 from 89 (R=Et) and... 

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