Hydroiodic acid catalyst

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

Iodine is known to catalyze the condensation of aldehydes, benzyl carbamate and allyltrimethylsilane to homoallylic amines. However, in this case the involvement of an in sitn prepared [MejSi] species was suggested to be the active catalyst [235], An iodine catalyzed acetalization of carbonyl compounds was reported, where the active catalyst was believed to be hydroiodic acid [236],... 

Table 1 Catalysts used for the dehydration of polysaccharides Organic acids Oxalic acid, levulinic acid, maleic acid, p-toluenesulfonic acid Inorganic acids Phosphoric acid, sulfuric acid, hydrochloric acid, iodine, or hydroiodic acid generated in situ...

It is known that certain Friedel-Crafts acylations of reactive aromatics may proceed with a small amount of catalyst or even, to some extent, with no catalyst at all.41 Effective catalysts are Fe, FeCl3, ZnCl2, iodine, and hydroiodic acid. However, satisfactory yields are usually obtained with activated and polynuclear aromatics, and heterocycles. The mixed anhydrides acyl triflates are also powerful acylating agents without catalyst.34... 

Over 35 years ago, Richard F. Heck found that olefins can insert into the metal-carbon bond of arylpalladium species generated from organomercury compounds [1], The carbopalladation of olefins, stoichiometric at first, was made catalytic by Tsutomu Mizoroki, who coupled aryl iodides with ethylene under high pressure, in the presence of palladium chloride and sodium carbonate to neutralize the hydroiodic acid formed (Scheme 1) [2], Shortly thereafter, Heck disclosed a more general and practical procedure for this transformation, using palladium acetate as the catalyst and tri-w-butyl amine as the base [3], After investigations on stoichiometric reactions by Fitton et al. [4], it was also Heck who introduced palladium phosphine complexes as catalysts, enabling the decisive extension of the ole-fination reaction to inexpensive aryl bromides [5],... 

The benzylisoquinolines represent one of the largest group of plant alkaloids (146,147), and catecholic representatives occur in mammalian tissues and fluids. The best known is tetrahydropapaveroline, shown in Fig. 22 as the (5) enantiomer TIQ 75a. Racemic material is often referred to as THP (160,161). The synthesis of TIQ 75a as well as that of the plant alkaloid (5)-N -bisnorreticuline (77a) is shown in Fig. 22. (5)-Tetrahydropapaverine (74a), on treatment with concentrated hydroiodic acid at 125 C, afforded TIQ 75a, which was fully characterized as its hydrochloride (156). TIQ 77a, possibly an intermediate in the plant biosynthesis of (5)-norreticuline (78a) and derived TIQs, and possibly mammalian morphine as well, was prepared from the benzyl-protected TIQ 76a. Deblocking was achieved over Pd catalyst and hydrogen in the presence of hydrochloric acid, leading directly to the hydrochloride salt of TIQ 77a... 

Homologation of methanol catalysed by 1 and 2 in presence of iodide promoter hydroiodic acid (entry Nos. 1 and 3), gave dimethyl ether selectively and while in the presence of water along with hydroiodic acid ( entry Nos. 2 and 4), both catalyst systems favoured the formation of acetic acid and dimethyl ether as the products. Catalyst 2 also gave methyl acetate a product of esterfication of acetic acid by methanol. Homogeneous catalyst 1 is at least two times more reactive than 2 in presence of water, however, catalyst 2 is more selective towards the formation of acetic acid (80%). 

Krishna and Jain have synthesized 3-nitrophenothiazine 120 from 4-nitrodiphenyl-amino-2-sullinic acid 119 and H2SO4. Similarly, Evans and Smiles (35JCS1263) have obtained the same compound by using hydroiodic acid as a catalyst (Scheme 56). 

Schappacher and Deffieux [93] first reported the cyclization from heterodifunctional linear polymers. The linear precursor was made from 2-chloroethyl vinyl ether (CEVE) by living cationic polymerization from a styryl vinyl ether with hydroiodic acid and ZnCl2 as catalyst combination. By treating with SnCLi, the iodo endgroup was converted to carbocation and coupled to the styrene chain end to form the cyclic polymer (Scheme 24). With the same strategy, they successfully synthesized a series of cyclic polymer derivatives based on the monomer CEVE. 

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