Iodine as catalyst

Diacetone alcohol is readily dehydrated by adding a very small quantity of iodine as catalyst and distilling slowly ... 

However, since 1970 the preferred method of acetic acid manufacture is carbonylation of methanol (Monsanto process), involving reaction of methanol and carbon monoxide (both derived from methane) with rhodium and iodine as catalysts at 175°C and 1 atm. The yield of acetic acid is 99% based on methanol and 90% based on carbon monoxide. 

Sulfur chloride is prepared as an orange liquid by passing chlorine gas through molten sulfur. If excess chlorine is passed and in the presence of a trace FeCls or iodine as catalyst, an equilibrium mixture of about 85% dichloride, SCI2, and 15% S2CI2 is obtained. The dichloride dissociates to sulfur chloride ... 

P. Jolibois found that the velocity of transformation of yellow to red phosphorus increases with the temp. It is very slow at 360°, b.ut it can be observed at 250° if a trace of iodine as catalyst be... 

PiCHO + H2NC6H4N(CH3)2 This is the favored procedure for preparing the aldehyde (Refs 11 24). Reaction (A) is done at room temp in pyridine, using iodine as catalyst (Ref 11), or in alcohol-acetone mixt with anhyd Na carbonate as catalyst (Ref 24) earlier procedures (see refs cited in Vol 2, B35-R) are reported to be unsatisfactory (Ref 11). Reaction (B) proceeds in strong aq hydrochloric acid overall yields are 39—52%. Reaction (A) proceeds in 80% yield in aq medium in the presence of light (Ref 90), with less by-product formation than noted in the other methods... 

Ketones, I COR2, have been converted to their -dihydroperoxides (112) using a green oxidant, aqueous 30% hydrogen peroxide, with iodine as catalyst.337 The iodine may enhance the electrophilic character of the carbonyl carbon and/or the nucleophilicity of the hydrogen peroxide. The reaction has also been extended to... 

In the tin tetrachloride-catalyzed acetylation by acetic anhydride in dichloroethane, furan is more reactive than thiophene by a factor of 11.9 as determined by a competitive method. The use of iodine as catalyst does not substantially alter the reactivity ratio.130 The comparison could not be extended to pyrrole, because of the interaction of this substrate with Friedel-Crafts catalysts139 (see discussion in Section II, E). 

Iodide, 121 Iodination, 77 of A-4-thiazoline-2-one, 402 Iodine, as catalyst of rearrangement, 406 Ionization potential, relation with nucleophilic reactivity of A-4-thiazoline-2-thione, 384... 

P-Hydroxy ketones. a-Bromo ketones undergo a Reformatsky-type reaction with aldehydes which is promoted by R3Sb but which is only possible with iodine as catalyst. The function of I2 is probably for a Br/I exchange, since I2 is not required in reactions with a-iodo ketones. 

Very simple and efficient Michael reaction of indoles 449 with cyclic and acyclic unsaturated ketones has been accomplished in the presence of only 1 mol% of iodine as catalyst at room temperature under solvent-free conditions (Equation 106) <2005TL2479>. 

Simple cyclooctatetraenediyls [M(C8H8)] (M = Eu, Yb) can be made by reaction of cyclooctatetraenewith solutions ofthe metal in liquid ammonia. Another route to [M(CsH8)] (Sm, Yb) is the reaction of the metals with cyclooctatetraene using iodine as catalyst. These compounds are not monomers, but the Lewis base adduct [M(C8H8)(py)3] has a piano-stool structure. 

Ammonium hexanitratocerate(IV) as a standard oxidant for reactions at room temperature has been developed for several substances. " Oxalate can be titrated with Ce(IV) in 0.5 M HNO3 with an iodide catalyst mandelic acid at a lower acid concentration, 0.1 MHNO3 Mn(II) with excess Ce(TV) in 0.5 to 2M HNO3 with silver nitrate catalyst hydrazine or isonicotinic acid in HCl-KBr solution and As(III) in HCl, HNO3, or H2SO4 solution with a trace of iodine as catalyst. 

By the action of chlorine on benzyl chloride, in presence of iodine as catalyst, />-chlorobenzyl chloride is formed ... 

Methylpyrazine heated with dimethylformamide and sulfur in o-dichloro-benzene at about 150-180° (with and without iodine as catalyst) gave 2-N-methyl(thiocarbamoyl)py razine and 2-A, yV-dimethyl(thiocarbamoyl)pyrazine (1268,... 

These include amitraz (110), prepared from 54, a member of the form amidine class, active against mites and ticks, that have replaced organophosphorus compounds. Notably, amitraz is active against newer strains of pyrethroid-resistant ticks. The reaction of diphenylamine (8) with sulfur in the presence of iodine as catalyst yields the anthelmintic (worming agent) phenothiazone (phenothiazine) (111) (Scheme 24). It is too toxic for human use, though it is an intermediate in the production of antipsychotic drugs. 

Dehydration. In one example, illustrating the efficiency of iodine as catalyst for dehydration, a solution of 100 g. of benzopinacol in 500 ml. of acetic acid is treated... 

Cyclopropanes can be synthesized from many organic gem-dihalides using copper and a trace of iodine as catalysts.37 This procedure is comparable to the Simmons-Smith reaction in yields and is more convenient because of a wider range of substrates available. 

A supplementary note on Iodine as catalyst for dehydration calls attention to the interesting finding that perchloric acid is a superior reagent for the rearrangement... 

Most group VIII metals will, to some extent, catalyze carbonylation. Early work utilized Ni and iodine as catalyst. Using metal iodides on silica as carbonylation catalysts at 175-230°C, —27 MPa, and a 2 hr residence time shows the reactivity order Ni > Co... 

The treatment of glutarimide (586) with two equivalents of r-butyldimethylsilyl triflate (587) in the presence of Et3N gives rise to 2,6-bis(t-butyldimethylsiloxy)-3,4-dihydropyridine (588) (equation 297)330. Quinone (589) and hexamethyldisilazane (405) in the presence of iodine as catalyst form l,4-bis(TMS)-hydroquinone (590) (equation 298)331. 

Trichloromethanesulfenyl chloride (5) is a yellow oily substance, volatile with steam, having a very unpleasant odour, with a boiling point of 146-149°C. It is prepared by the chlorination of carbon disulfide below 30°C in the presence of iodine as catalyst (Klason, 1887) ... 

Knoevenagel1045 used iodine as catalyst and obtained an 87% yield of pure diethylaniline by heating aniline (18.6 g), ethanol (36.8 g), and iodine (0.5 g) at 220-230° for 10 h. Numerous further examples are recorded in the same paper.1045... 

Protection and deprotection of functional groups. Alcohols and their tetrahydro-pyranyl ethers are interconverted with iodine as catalyst. Etherfication is done in a nonhydroxylic solvent, whereas the ether cleavage is achieved in MeOH. 

Esterification. Carboxylic acids can be esterified by oxidation of a hydra-zone with peracetic acid with a trace of iodine as catalyst (equation I). This... 

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