Aryl halides silver® oxide

The reaction can be performed at room temperature with various heteroaryl halides (Equation 73) <20050L697>. It was found that (2-pyridyl)allyldimethylsilanes are pyridyl-transfer reagents in palladium-catalyzed coupling reactions of aryl iodides in the presence of silver oxide as an activator <20060L729>. 

Alkylation of2-aryl-I, 4-oxadiazoles. Alkylation of 2-aryl-l,3,4-oxadiaaoles (I) by alkyl halides in acetonitrile in the presence of silver oxide gives O- and N-alkyl... 

Sulfonic esters are most frequently prepared by treatment of the corresponding sulfonyl halides with alcohols in the presence of a base. This procedure is the most common method for the conversion of alcohols to tosylates, brosylates, and similar sulfonic esters. Both R and R may be alkyl or aryl. The base is often pyridine, which functions as a nucleophilic catalyst, as in the similar alcoholysis of carboxylic acyl halides (16-61). Propylenediamines have also been used to facilitate tosylation of an alcohol. Silver oxide has been used, in conjunction with KI. Primary alcohols react the most rapidly, and it is often possible to sulfonate selectively a primary OH group in a molecule that also contains secondary or tertiary OH groups. The reaction with sulfonamides has been much less frequently used and is limited to A,A-disubstituted sulfonamides that is, R— may not be hydrogen. However, within these limits it is a useful reaction. The nucleophile in this case is actually RO . However, R may be hydrogen (as well as alkyl) if the nucleophile is a phenol, so that the product is RS020Ar. Acidic catalysts are used in this case. Sulfonic acids have been converted directly to sulfonates by treatment with triethyl or trimethyl orthoformate, HC(OR)3, without catalyst or solvent and with a trialkyl phosphite, P(OR)3. ... 

METHYL SULFOXIDE (67-68-5) CjHjOS (CHjIjSO Combustible liquid [explosion limits in air (vol %) 2.6 to 63.0 flashpoint 203°F/95°C oc autoignition temp 419°F/215°C Fire Rating 2]. Violent or explosive reaction with strong oxidizers, acryl halides, aryl halides and related compounds, alkali metals p-bromobenzoyl acetanilide, boron compounds, especially hydrides iodine pentafluoride, magnesium perchlorate, methyl bromide, perchloric acid, periodic acid, silver fluoride, sodium... 

The facile intramolecular oxidative addition of aryl halide which leads to Pd(IV) complex 22 (see Scheme 2.5) provided the basis for the development ofa special type of Pd(II)/Pd(IV) Heck reaction [58,109]. Although 22 fails to react with methylacrylate at room temperature, an insertion reaction leading to the corresponding Heck product takes place in the presence of AgCl04, which removes a iodide ligand generating the required coordination vacancy. Thus, complex 22 (10 mol%), or its Pd(II) precursor 20, catalyzes a Heck-type couphng of 2-iodobenzoic acid with methyl acrylate, driven by iodide precipitation with silver salts (Eq. (2.10)). The reaction is completed within about 3.5 h at room temperature and, in contrast with the... 

The first report of the oxidative addition of zinc metal to organic halides dates back to the work of Frankland [1-4] around 1850. He discovered that dialkylz-inc compounds could be prepared from zinc metal and methyl iodide or ethyl iodide. However, the reaction did not proceed with alkyl bromides or chlorides. Also, no aryl halides were found to undergo the oxidative addition reaction. Several approaches have been reported since that time to increase the reactivity of the zinc metal. The majority of these modifications have employed zinc-copper couples [5-8] or zinc-silver couples. However, all of these procedures still only worked with alkyl iodides. Noller used a mixture of alkyl iodides and bromides but found that the mixture must contain a large percent of alkyl iodide [9]. 

We reasoned that such a decarboxylation step could also be employed in a redox-neutral cross-coupling reaction with carbon electrophiles. On this basis, we drew up a catalytic cycle that starts with an oxidative addition of aryl halides or pseudohalides to a coordinatively unsaturated palladium(O) species f (Scheme 5). The more weakly coordinating the leaving group X, the easier should be its subsequent replacement by a carboxylate. At least for X = OTf, the palladium(ll) carboxylate h should form quantitatively, whereas for X = halide, it should be possible to enforce this step by employing silver or thallium salts as species g. The ensuing thermal decarboxylation of the palladium(ll) intermediate i represents the most critical step. Myers results indicated that certain palladium(ll) carboxylates liberate carbon dioxide on heating. However, it remained unclear whether arylpalladium (II) carboxylate complexes such as i would display a similar reactivity. If this were to be the case, they would form Ar-Pd-Ar intermediates k, which in turn are... 

This first plan for a decarboxylative cross-coupling carried with it certain weaknesses for potential industrial applications. It was to be expected that the salt metathesis between alkali metal carboxylates and late transition metal halides would be thermodynamically disfavored. We expected the formation of a palladium benzoate complex i from palladium bromide complexes c and potassium benzoate (g) to proceed well only in the presence of a stoichiometric quantity of silver to capture bromide ions [27]. However, we did not like the idea of using stoichiometric quantities of silver salts or of expensive aiyl triflates in the place of aryl halides. Finally, the published substrate scope of the oxidative Heck reactimi led to concerns that palladium catalysts mediate the decarboxylation rally of a narrow range of carboxylates, precluding use of this reaction as a general synthetic strategy. 

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