Alkenes silver® nitrate

Alkylboranes can be coupled by treatment with silver nitrate and base." Since alkylboranes are easily prepared from alkenes (15-16), this is essentially a way of coupling and reducing alkenes in fact, alkenes can be hydroborated and coupled in the same flask. For symmetrical coupling (R = R ) yields range from 60 to 80% for terminal alkenes and from 35 to 50% for internal ones. Unsymmetrical coupling has also been carried out, but with lower yields. Arylboranes react similarly, yielding biaryls. The mechanism is probably of the free-radical type. 

Stationary phases can be made highly selective by adding compounds to them which have affinities for certain chemical species. For example, silver nitrate, incorporated into a polar liquid preferentially retards the elution of alkenes by formation of weak -complexes. A selection of stationary phases with their maximum operating temperatures and useful applications is given in Table 4.10. 

Other polymerisation incidents are f Acrylaldehyde, 1145 Acrylamide, 1180 Acrylic acid, 1148 Acrylic acid, Initiator, Water, 1148 f Acrylonitrile, 1107 f Acrylonitrile, Initiators, 1107 f Acrylonitrile, Silver nitrate, 1107 f Acryloyl chloride, 1093 Allyl 4-toluenesulfonate, 3315 Aluminium chloride, Alkenes, 0062 3 - Aminopropiononitrile f Aziridine, Acids, 0863... 

Bis [(trifluoromethyl)thio] acetaldehyde (83a) has been prepared from an enam-ine precursor (84), although refluxing in aqueous ethanolic HCl is required to effect this reaction.The aldehyde is less stable than its enol tautomer (83b), and many reactions typical of aldehydes fail. For example, addition of aqueous silver nitrate immediately yields the silver salt of (83b), rather than giving precipitation of (elemental) silver. The (trifluoromethyl)thio substituent has pseudohalogenic character and, together with the hydroxy group, stabilizes the alkene tautomer in the manner of a push-pull alkene. The enol-aldehyde equilibrium mixture in acetonitrile shows an apparent of 2.6 when titrated with aqueous hydroxide. 

When the reaction of methyl 5,6-dideoxy-2,3-di-0-p-tolylsulfonyl-a-L-arafoino-hex-5-enofuranoside with silver nitrite and iodine was performed in more-polar solvents, such as methanol and acetonitrile, a /3-iodo nitrate was produced, in addition to the C-iodo-C-nitro adduct 88 in methanol, the ratio of the two products was130 3 2. The /3-iodo nitrate was identical with the adduct obtained by the reaction of the alkene with silver nitrate and iodine in acetonitrile.132 The formation of the /3-iodo nitrate in the silver nitrite-iodine reaction in polar solvents may be due to the increased solubility of the silver nitrite the available nitrite ions could then be oxidized to nitrates. The positions of the iodo and nitrate groups in the adduct have not yet been established. 

Some attempts to use simple Cu and Ag salts as catalyst for alkene epoxidation have been performed. Both silver nitrate and triflate in acetonitrile as the solvent were unsuccessful (ref. 9). However, we have found that Ag20 as well as AgN03, the latter in the presence of tertiary amines, can catalyze the oxidation of alkenes with iodosylbenzene as oxygen donor (ref. 10). The results for the epoxidation of different alkenes catalyzed by Ag20 and with iodosylbenzene as oxygen donor at 60 0 C in CHCI3 are given in Table 3. 

The addition of carboxylic acids to alkynes affords enol esters which are useful as intermediates in organic synthesis.470 As in the addition to alkenes, a catalyst is usually required for high conversions of alkynes to enol esters. Simple acid catalysis has been employed (equation 279),471 but the more common catalysts are Lewis acids, such as boron trifluoride etherate,472 silver nitrate,473 zinc acetate474 and zinc oxide (equations 280 and 281),47S-476... 

An equivalent reaction has been achieved via the treatment of hydroborated bisalkenes with alkaline silver nitrate solution (Table 1.4).22,23 This method has been used to synthesize a number of small and medium-size carbocyclic rings in moderate to good yield. The selectivity for terminal cyclization observed for 1,6-heptadiene and 1,7-octadiene indicates that, in these cases, hydroboration of each of the alkenes occurs independently to yield acyclic boranes. It has, however, been found that both cyclic and acyclic boranes react under these conditions to yield the ring-closed products (Scheme 1.3). 

The oxidative decarboxylation of aliphatic carboxylic acids is best achieved by treatment of the acid with LTA in benzene, in the presence of a catalytic amount of copper(II) acetate. The latter serves to trap the radical intermediate and so bring about elimination, possibly through a six-membered transition state. Primary carboxylic acids lead to terminal alkenes, indicating that carbocations are probably not involved. The reaction has been reviewed. The synthesis of an optically pure derivative of L-vinylglycine from L-aspartic acid (equation 14) is illustrative. The same transformation has also been effected with sodium persulfate and catalytic quantities of silver nitrate and copper(II) sulfate, and with the combination of iodosylbenzene diacetate and copper(II) acetate. ... 

Fluorine can also be added to alkenes by reaction with a solution of anhydrous hydrogen fluoride in pyridine (Olah s reagent) containing either Af-brotno- or A -iodosuccinimide, or iodine or bromine and silver nitrate. The final addition of silver fluoride to the reaetion mixture leads to the formation of vicinal difluorides 19,23.153... 

Sulfonic acids add to alkenes and alkynes. The reaction of an alkyne with ara-toluenesulfonic acid and treatment with silica gives the vinyl sulfonate (C=C—OS02To1) Cyclic sulfonates can be generated by the reaction of an allylic sulfonate salt (C=C—C—OSOs ) with silver nitrate in acetonitrile containing an excess of bromine and a catalytic amount of water. Sultones are formed when alkenes react with PhlO and two equivalents of Me2SiS03Cl. ... 

Silver chromate, Ag2Cr04, a reddish-brown precipitate prepared by adding an aqueous solution of silver nitrate to an aqueous solution of potassium chromate, is used with iodine for the preparation of a-iodo-ketones from alkenes [616]. 

Silver nitrate— ethylene glycol Specific for cis and. trans alkenes 50... 

It is also possible to modify the adsorption properties of the silica gel by incorporating substances such as bases or buffers enabling coatings with accurately defined pH to be prepared. In a like manner silver nitrate can be added this admixture changes the adsorptive properties to permit increased discrimination and separation of unsaturated compounds, especially alkenes. The technique is commonly known as Argentation TLC. 

Instead of silver nitrate, Pagni, Kabalka and coworkers used activated and even out-of-the-bottle y-alumina to promote electrophilic additions of iodine to alkynes (cf. the alumina-catalysed addition of HI). ( )-l,2-diiodoalkenes were obtained in 50-98% yield. With terminal alkynes and unactivated alumina, moreover, a minor amount of 1,1,2-triiodo-l-alkene was detected it was the product of iodine addition to intermediate 1-iodo-1-alkyne. Still another method of electrophilic addition of iodine to alkynes involves mercury(II) salts in dichloromethane at 0 °C. ... 

E)-Alkenes. The reaction of trialkylboranes with alkaline silver nitrate (2, 368) to form coupled alkanes has been used to convert 1,2-diorganoboranes from internal alkynes into (E)-alkenes. The reaction is considered to involve an intermediate diradical that couples intramolecularly to the alkene. 

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