Materials iodobenzene

The de Meijere group [63] prepared interesting spiro-compounds containing a cyclopropyl moiety using a combination of a Heck and a Diels-Alder reaction, with bicyclopropylidene 6/1-115 as the starting material. The transformation can be performed as a three-component process. Thus, reaction of 6/1-115, iodobenzene and acrylate gave 6/1-116 in excellent yield. With vinyliodide, the tricyclic compound 6/1-117 was obtained (Scheme 6/1.31). Several other examples were also described. 

Treatment of a solution of 55cCu(OTf)2 complex with a stoichiometric amount of PhI=NTs in CH2C12 resulted in rapid uptake of the insoluble iodinane. This complex, when treated with styrene, provided aziridine in quantitative yield in the same selectivity (37% ee) as the catalytic reaction (in CH2C12 at 25°C, 36% ee), Eq. 59. Addition of toluene at -78°C resulted in deposition of the complex as an oil. Analysis of the supernatant liquid revealed that <5% Phi was present, suggesting that the iodobenzene was still part of the complex. Unfortunately, this material resisted repeated attempts at crystallization. Whatever its true nature, it seems that this complex is not a classical copper nitrenoid (77). 

Iodoxybenzene.—The major portion of the iodosobenzene so prepared is made into a paste with a little water and submitted to steam distillation in a round-bottomed flask. The distillation is continued until all the material has dissolved and the iodobenzene produced has passed over (use a condenser and receiver). The residue after the distillation (if still turbid) is filtered while hot and the filtrate is concentrated on the water bath until a sample, poured... 

The phenyl u-anion is strongly basic but may be obtained at relatively modest potentials by reductive cleavage of haloben-zenes when the right cathode material is chosen [63]. Typically, the reactions are carried out at constant current in undivided cells using Cd-coated Ni-cathodes, A1 or Mg sacrificial anodes, DMF (or MeCN for cyanomethylation) as the solvent and BU4NBF4 as the electrolyte. Under these conditions, iodobenzene is reduced at —1.6 V versus SCE and bromobenzene at —1.9 V, which may allow their use in situ [63, 91-93]. 

Neutral alumina (1.5 g) was thoroughly mixed with iodobenzene diacetate (532 mg, 1.65 mmol) and benzyl phenyl sulfide Id (300 mg, 1.5 mmol) using a pestle and mortar. The adsorbed material was placed in an alumina bath inside the microwave oven and irradiated at 50% power for two successive intervals of 45 s each (with time interval of 3-4 min bath temperature rose to 80-85 °C). The progress of the reaction was monitored by TLC (hexane-ethyl acetate, 7 3, v/v). When the reaction was complete the whole material was directly charged onto a silica gel column which provided iodobenzene on elusion with hexane (100 mL). The fractions eluted by chloroform-hexane (1 1 v/v) provided sulfone (<7% by... 

For the Heck reaction as discussed in Section III.2.1 the final position of the olefi-nic double bond of the products must not necessarily be the same as in the starting materials (for example Schemes 8, 9, and 10 of Section III.2.1) [1], The selectivity is often driven by stereochemical requirements, because the /1-hydrogen elimination step which forms the double bond proceeds exclusively in a syn manner (if a trans /3-hydrogen is eliminated, one should suspect major deviations from the general mechanism of the Heck reaction, for example electrophilic substitution instead of carbopalladation). An impressive example of a double bond migration is depicted in Scheme 1 - instead of olefins the coupling reaction of iodobenzene 1 with the olefmic alcohol 2 results in the isomeric aldehydes 3 and 4 as final products [2], Reactions of this type have emerged as valuable tools for the synthesis of carbonyl compounds and also as crucial steps in domino processes. 

As shown in other sections of this chapter, overall attention has shifted from diazonium salts as aryl radical sources to bromo- or iodobenzenes. One of the few recent attempts to improve the classical Pschorr cyclization using diazonium ions as starting materials led to the discovery of new catalysts [119]. Results from a first samarium-mediated Pschorr type show the variety of products that can be expected from intramolecular biaryl syntheses under reductive conditions (Scheme 22). Depending on the substitution pattern of the target aromatic core and the reaction conditions, either the spirocycle 60, the biphenyl 61, or the dearomatized biphenyl 62 were formed as major product from 63 [120]. 

In most cases iodobenzene or some ring-substituted analogues, especially iodoben-zoic acid, are the starting materials through which hypervalent iodine reagents are prepared. It is emphasized that most preparations are very convenient, so that it is not necessary to purchase commercially available compounds these and their suppliers include ... 

Although several methods are available for the preparation of the title compounds, in practice the starting material is (diacetoxyiodo)benzene (DIB). The standard method for its preparation is direct oxidation of iodobenzene with either peracetic acid [ 1 ] or sodium perborate in acetic acid [2], The first method appears to be preferable it requires great care in maintaining temperature at exactly 40°C at a lower... 

A stirred mixture of acetic anhydride (305 ml) and 30% hydrogen peroxide (70 ml) was kept at exactly 40°C for 4 h the use of a thermostated bath is strongly recommended. To the resulting peracetic acid solution, iodobenzene (52 g, 28.5 ml) was added with stirring over 15 min and the clear reaction mixture was kept overnight at room temperature. A part of DIB crystallized out and was collected then ice-water ( 400 ml) was added to the filtrate and a further crop of crystals was obtained. The combined material was washed with cold water and petroleum ether and was dried in a desiccator over sodium hydroxide to yield 55-65 g (67-79%) of crude DIB, m.p. 156-159°C (recrystallized from chloroform, m.p. 163-165°C) this purity is satisfactory in most cases. 

Depending on the reaction conditions, halogenation of thieno[2,3-Z>]pyridine (20) can lead to a variety of products resulting from substitution, addition, and oxidation reactions. 2,3-Dibromo-thieno[2,3-/)]pyridine is produced by the reaction of compound (20) with bromine in an aqueous carbon tetrachloride system and the 2,3-dichloro-2,3-dihydro derivative is formed from the same starting material upon treatment with chlorine in chloroform/water or with iodobenzene dichloride in aqueous acetonitrile (70JHC81, 71JHC931). 

In a large mortar chilled in an ice bath are placed 55 g. (0.2 mole) of iodobenzene dichloride (p. 69), 50 g. of anhydrous sodium carbonate, and 100 g. of finely crushed ice. The mixture is ground thoroughly (Note 1) until all the ice has melted and a thick paste results. To this suspension 140 cc. of 5 N sodium hydroxide is added, in 20-cc. portions, with repeated trituration after each addition. Finally, 100 cc. of water is added to render the mixture more fluid and the material is allowed to stand overnight. The product is collected with suction, pressed thoroughly on the filter, transferred to a beaker, and washed thoroughly with i WiUgerodt, J. prakt. Chem. (2) 33, 155 (1886). 

A three-component domino reaction catalyzed by palladium that produces 4,5-disubstituted dihydrobenzo[ ]furans from readily available starting materials has been developed by Pache and Lautens. The reactions of iodobenzenes of type 61 with Bui and tert- mx acrylate, as shown, give good yields of cyclization products (Scheme 96) <2003OL4827>. A reaction mechanism which involves sequential alkylation-alkenylation has been proposed. 

Diaryliodonium compounds can be prepared by acid-catalyzed condensation of iodoso aryls with another aryl molecule (equation 129). Another method is the use of iodine trichloride in reaction with organometalUc compounds (equations 130 and 131). RICI2 may be prepared by direct chlorination of RI (R = CF3CH2, CHF2(CF2)sCH2) and these materials can be used to chlorinate iodobenzene to give the less hydrolytically stable compound PhICl2. ... 

A mixture of 200 g. (1.0 mole) of phenothiazine, 306 g. (1.50 mole) of iodobenzene, 120 g. of anhydrous sodium carbonate, and 10 g. of copper powder is stirred and heated to reflux for 12 hours. The reaction mixture is steam-distilled until all steam-volatile material has been removed. The solid residue remaining in the steam-distillation vessel is separated, dried, and distilled to give 176 g. (64%) of 10-phenylphenothiazine boiling at 220-223°/ mm. and melting at 92 93°. Recrystallization from glacial acetic acid gives white prisms melting at 94.5°. 

Phenylation of carbanions derived from olefins such as 1,3-pentadiene and l-(p-anisyl) propene and aromatics such as indene and fluorene are possible by the SrnI route in ammonia solvent. From the 1,3-pentadiene a mixture of mono-olefins and dienes is produced along with a small amount of di- and triphenylated material. Hydrogenation of the mixture gives 1-phenylpentane in 74% yield.106) Phenylation of 2- and 4-picolyl anions is conveniently effected in ammonia. When bromo- or iodobenzene is used for this purpose, reaction probably occurs by both SrnI and benzyne routes.111)... 

Butyllithium (9.5 mL, 15 mmol, 1.6 M solution in hexane) was added to a solution of furan (1.1 mL, 15 mmol) in THF (15 mL) at 0 °C. After stirring at 0 °C for 1 h and room temperature for 1 h, the yellow solution was slowly transferred via cannula into a solution of zinc chloride (15 mL, 15 mmol, 1 M solution in Et20) at 0°C. The mixture was stirred for 1 h at 0 °C and then added to a solution of l-bromo-2-iodobenzene (1.3 mL, 10 mmol) and bistriphenylphosphine palladium chloride (0.21 g, 0.3 mmol) in THF (2 mL). After stirring for 12 h at room temperature, the reaction was added to IM HCl aqueous solution (10 mL) and the product was extracted into ether and washed with saturated aqueous sodium bicarbonate solution. The ether solution was dried (MgS04) and the solvent was removed in vacuo. The crude material was purified by flash chromatography (hexane) to give 2.10 g (95%) of the l-bromo-2-(2 -furyl)-benzene 5.3a as a colorless oil. 

As mentioned before structure of 2-2 was proposed by spectral analyses, the position of methylenedioxyl group in isoquinoline of 2-2 is in position C-5—C-6, but it did not exclude its possibility in position C-7—C-8. A total synthesis was accomplished in order to confirm the structure and to derive more samples for pharmacological tests. Piperonal 2-4 was used as starting material. It was oxidized by silver oxide in basic condition to get 2-5, then amidized with dimethyl amine to 2-6 and directed ortho-lithiation with n-butyl-lithium in THF (tetrahydrofuran) to get homogeneous yellow solution, which upon treatment with methyl iodide afforded toluamide 2-7, the yield was 85%. The model synthesis study showed that lithiated toluamide 2-7 could condense with compound 2-14 to achieve the final product 2-2 through several steps (see below). The intermediate compound 2-14 could be synthesized starting from the same piperonal 2-4. It was reacted with cyclohexylamine to get Shiff base 2-8, the latter was reacted with 1.13 equiv. of n-butyllithium at -78°C, the metalated intermediate was carbethoxylated in situ by addition of excess ethyl chloroformate and the aldehyde 2-9 was obtained by extraction with dilute acid. Combination of 2-9 with equimolar of propane-1,3-dithiol a compound 2-10 was obtained, then 2-10 was reduced by lithium aluminum hydride and benzylated with benzyl bromide to 2-12. After treatment with bis(trifluoroacetoxy) iodobenzene, the obtained compound 2-13 was reacted with benzylamine to get the key compound 2-14. 

To convert labdanolic acid (8.27) to the naphthofuran (8.10), it is necessary to shorten the side chain and then cyclise the residue onto the alcohol to form the furan ring. In this synthesis, Bolster and de Groot carried out the chain shortening in two steps.816 Firstly, after protection of the ring hydroxyl group by conversion to the acetate, the terminal acidic carbon atom was removed by photo-decarboxylation in the presence of iodine and iodobenzene diacetate. This gave the iodinated material (8.29). Treatment of (8.29) with potassium tert-butoxide... 

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