Aryl lithium reagents

When an aminophosphonium species is used with an aryl lithium reagent, cleavage of the amino functionality from phosphorus is observed, producing the parent phosphine.10 This reaction has been used to prepare stable phosphoranes from aminophosphonium species using dilithium reagents (Figure 5.6).10 It should be noted that the... 

Protonic acids and some other electrophiles cause the aromatization of naphthalen-l,4-imines and of derivatives of the related 1,4-epoxy-1,4-dihydronaphthalene ring system (126) to naphthalene derivatives (see Section III,F), and simple electrophilic addition to the 2,3-double bond has not been observed. Ring-opening of the ether (126) also occurs on addition of alkyl or aryl lithium reagents as a result of exo attack by the nucleophile at the 2-position. ... 

Experimental enthalpies of formation for twelve alkyl- and aryl-lithium reagents were derived by Hohn from the enthalpies of reaction 5 in which the organolithium reagents were dissolved or suspended in ether or in petroleum ether. 

Tertiary and aromatic nitroso compounds react with aryl Grignard or aryl-lithium reagents giving the corresponding hydroxylamines . This reaction is useful for preparation of alkyl- and aiylhydroxylamines (e.g. 109, equation 80 and 110, equation 81) and can be considered as complementary to arylation of hydroxy lamines with activated aryl halides. It has been used for functionalization of cyclophanes with the hydroxy amino group. The main limitation of the reaction is the relatively restricted choice of available aliphatic nitroso components, so most of reactions were done with 2-nitroso-2-methylpropane. There is no literature data about the possibility of removal of the tert-butyl group from these compounds. 

The first general method allowing the preparation of optically active 3,3-dialkylpropionic acids via asymmetric synthesis is based on chiral oxazolines.37-41 The a,3-unsaturated derivatives (41), accessible as pure ( )-isomers from (40) and the respective aldehydes (RCHO), undergo highly selective 1,4-additions in a variety of cases (Scheme 16) when treated with alkyl- or aryl-lithium reagents. The products... 

Reductive coupling of iodonium salts catalysed by a palladium-zinc system also produced biaryls in good yield [38]. Also very effective was the palladium-catalysed cross-coupling of iodonium salts with sodium tetraphenylborate in water [39]. The reaction of 3-indolyl phenyliodonium trifluoroacetate with several alkyl and aryl lithium reagents gave 3-substituted indoles [40] ... 

These important compounds with regards to their reactivity are obtained by transmetalation see Transmetalation) between the appropriate metallocene dichloride (see Metallocene Complexes) and an alkyl- or aryl-lithium reagent. Dialkyl and diaryl zirconium complexes are very moisture-sensitive, degrading to form /r-oxo species (see Section 5). 

A major route to arynes and hetarynes proceeds by dehydrohalogenating molecules which are deactivated with respect to substitution by an SnAt mechanism. Frequently employed bases are amide and alkylamide ions, alkyl and aryl lithium reagents and tew-butoxide ion. In spite of various claims this approach has not been used successfully to generate a 5-membered hetaryne.68,7S)... 

Equilibria in mutual halogen-lithium exchanges have been measured67 to determine the relative stabilities of various alkyl-, cycloalkyl-, alkenyl-, and aryl-lithium reagents. 

There is a rather useful reaction with amides. Organolithium reagents react with DMF to give aldehydes.. An example is the reaction of 231 with s c-butyllithium to give the aryl-lithium reagent (see sec. 8.5.F for directed ortho metalation reactions). Subsequent reaction with DMF and hydrolysis gave a 91% yield of aldehyde 232 in Yamaguchi s synthesis of the radulanins. ... 

To functionalize the C5 position, Williams and Fu developed a 2-phenylsulfonyl substituted oxazole. The C5 position of this oxazole can be cleanly deprotonated with LDA and trapped with either NIS or NBS to form the 5-iodo- or 5-bromo-2-phenylsulfonyloxazole in good yield. The same report details that the 2-phenylsulfonyl group can subsequently be displaced with alkyl, alkenyl, or aryl lithium reagents to form 2,5-disubstituted oxazoles efficiently. A triflate at the C5 position can be prepared from the corresponding oxazolone however, the oxazolone decomposes at room temperature, and Kelly reported that attempted Stille coupling with C5 triflates failed due to decomposition of the triflate. ... 

M—C TTT 0 and are susceptible to nucleophilic attack (p.332). Alkyl and aryl-lithium reagents add to a carbonyl group of the hexacarbonyls M(CO) (M = Cr. Mo, W) to give an anionic species which can be formulated either as an acyl or a carbene complex. Treatment with a strongly electrophilic trialkylox-onium salt (a source of R" ) or protonation followed by methylation of the resulting hydroxycarbene derivative, affords the product. 

Fiaud et al. described the Pd(ii)-catalyzed coupling of optically active 2,5-diphenylphospholane oxide and aryl-/heteroaryl iodides in the presence of 1,3-bis(diphenylphosphanyl)propane (dppp) as the ligand and diisopropylethylamine as the base in DMSO (Scheme 25/1). l-Aryl-2,5-diphenylphospholane oxides were also prepared in another way, by the reaction of the corresponding phosphinoyl chloride with aryl lithium reagents (Scheme 25/2). 

Gassmann and his co-workers have synthesized several fused cyclopropanes [e.g. (14)] by reaction of (12) with excess of alkyl- or aryl-lithium reagents.The cyclopropene (13) is probably an intermediate in these reactions, and it is worth noting that cyclopropylmagnesium iodides [e.g. (16)] are produced by reaction of methylmagnesium iodide with cyclopropenes [e.g. (15)]. ... 

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