Iodobenzene, carbonylation

Organotin compounds such as aryl-, alkenyl-, and alkynylstannanes are useful for the ketone synthesis by transmetallation of acylpalladium 529 and reductive elimination of 530 as shown[389-393]. Acetophenone (531) is obtained by the carbonylation of iodobenzene with Me4Sn. Diaryl ketones... 

The carbonylation of iodobenzene with the benzylacetylene 580 affords the ( -3-arylidenebutenolide 582 by carbonylation of the benzoyl alkyne formed as a primary product[426]. The vinylpalladium 581 is formed by the addition of... 

A nickel(II) species is also though to be an intermediate in the carbonyla-tion reaction of iodobenzene with (V-methylbenzaldimine and nickel carbonyl. Two addition modes of an ensuing aroylnickel(II) complex to the C=N double bond can be envisaged as routes to l-methyl-2-phenylindol-3-one and an ethylenediamine derivative (Scheme 47).7 5 The scope of this simple indole synthesis has not been assessed. 

Alumina-sodium borohydride, reduction of carbonyl compounds with, 16 572-573 Alumina sols, gelation of, 23 77 Alumina-supported iodobenzene diacetate (IBD), 16 570... 

Additional examples of palladium-catalyzed cross-couplings, in particular with allenylzinc compounds, can be found elsewhere [11, 15, 36]. A systematic study comparing several chiral palladium phosphine catalysts in the reaction of 4,4-di-methyl-1,2-pentadienylzinc chloride and iodobenzene revealed that an enantiomeric excess of only 25% was obtained from the best catalyst combination PdCl2 and (R,R)-DIOP [15]. The synthetic value of these transformations of donor-substituted allenes as precursors is documented by the preparation of a/l-unsaturatcd carbonyl... 

An a-allenic sulfonamide undergoes Pd-catalyzed carbonylative cyclization with iodobenzene, affording a mixture of isomeric heterocycles (Scheme 16.12) [17]. The coupling reaction of an allene with a PhCOPdl species takes place at the allenyl central catrbon to form a 2-acyl-Jt-allylpalladium complex, which is attacked by an internal sulfonamide group in an endo mode, affording a mixture of isomeric heterocycles (Scheme 16.13). 

Several examples have been reported of the use of palladium-mediated oxidation reactions of alcohols and alkyl halides. Palladium(II) acetate in the presence of iodobenzene converts primary and secondary alcohols into carbonyl compounds under solid-liquid two-phase conditions [20], However, other than there being no further oxidation to carboxylic acids, the procedure has little to commend it over other methods. It is relatively slow with reaction times in the order of 2 days needed to achieve yields of 55-100%. 

Carbonylative coupling of iodobenzene with 2-methyl-3-butyn-2-ol under 65 bar carbon monoxide afforded phenylfuranones (double carbonylation) in reasonable yields (Scheme 6.32) [69]. The reaction is thought to proceed through the formation of a benzoylpalladium intermediate which either reacts with the alkynol or liberates benzoic acid hence the formation of considerable amounts of the latter. 

The step common to both of these reactions is electrophilic attack of a hypervalent iodine species at the a-carbon of the carbonyl compounds to yield an intermediate 3. Nucleophilic attack of methoxide ion or tosy-loxy ion with the concomitant loss of iodobenzene results in a-functionalized carbonyl compounds (Scheme 2). 

Scheme 12 Carbonylation of iodobenzene and formation of side products [34]...

In a later work by Skoda-Foldes et al. [34], the same microreactor X-Cube system [32] was employed to perform the double carbonylation of iodobenzene... 

Balogh J, Kuik A, Urge L et al (2009) Double carbonylation of iodobenzene in a micro-fluidics-based high throughput flow reactor. J Mol Catal A Chem 302(l-2) 76-79... 

An efficient dinuclear Pd catalyst 299 was developed for the double carbonylation of iodobenzene with diethyla-mine/ which substantially improved the process yield (98%) and product selectivity of A, A -diethylphenyl-glyoxamide 301 (96%) (Equation (26)). 

The double carbonylation of iodobenzene with diethylamine catalyzed by Pd(OAc)2-PPh3 was carried out in l-butyl-3-methylimidazolium tetrafluoroborate 315 as reaction medium at 80 °C and 38 atm of CO to give phenyl-glyoxamide 314 as the predominant product (83%) accompanied by benzamide 313 (17%) (Equation (29)). The use of ionic liquids showed the same reactivity and product selectivity as those using diethylamine as solvent for this reaction, while separation of products and recycling of the catalyst was easier. ... 

The carbonylation of o-diiodobenzene with a primary amine affords the phthalimide 501 [355,356], Carbonylation of iodobenzene in the presence of odiaminobenzene (502) and DBU or 2,6-lutidine affords 2-phenylbenzimida-zole (503)[357], The carbonylation of aryl iodides in the presence of pentafluor-oaniline affords 2-arylbenzoxazoles directly. 2-Arylbenzoxazole is prepared indirectly by the carbonylation of n-aminophenol[358]. The optically active aryl or alkenyl oxazolinc 505 is prepared by the carbonylation of the aryl or enol triflates in the presence of the opticaly active amino alcohol 504, followed by treatment with thionyl chloride[359]. 

Carbonyl complexes of nickel and perfluoroketonesin donor solvents are thermally stable against fluorine elimination. However, in the presence of iodobenzene loss of fluorine has been observed with a concomitant benzoylation at the carbonyl oxygen.213... 

The elimination of the hydridopalladium group to the allylic position causes the formation of 3-substituted carbonyl compounds when allylic alcohols are reacted with organic halides (39). For example, when iodobenzene is reacted with methallyl alcohol, 2-methyl-3-phenylpropanal was formed in 91% yield along with 4% of 2-methyl-2-phenylpropanal ... 

Keywords carbonyl compound, iodobenzene diacetate, microwave irradiation, a-organosulfonyloxylation... 

A mixture of carbonyl compound 1, iodobenzene diacetate (1.5 equiv.), and orga-nosulfonic acid (4.5 equiv.) was placed in a test tube placed inside the alumina bath and irradiated for 10-40 s at ten-second intervals in a domestic microwave oven at full power (600 W). After cooling at room temperature the mixture was extracted with dichloromethane (2x20 mL), washed with H20, and dried over MgS04. The mixture was evaporated and the residue was column chromatographed with ethyl acetate-hexane (1 3) to give the desired a-organosulfonyloxy carbonyl compound 2. 

Values of rate constants in reaction (18 a) have been calculated (40) by means of this and similar treatments for a-ketoacids (44, 45), pyri-dinecarboxylic acids (46, 47), unsaturated acids (48, 49), phthalic acid (50), carbonyl compounds (51,52), iodobenzenes bearing ionisable groupings (53), etc. 

A remarkable dual way to obtain PhI(02CCF3)0I(02CCF3)Ph involved either solvolysis of iodosylbenzene by trifluoroacetic acid or nucleophilic attack by a strong base to the carbonyl group of [bis(trifluoroacetoxy)iodo]benzene [49]. Another unusual reaction leading to the formation of the same iodane has been reported between iodobenzene and xenon bistrifluoroacetate [50]. 

In addition to allylic alcohols, other unsaturated alcohols react with halides to give carbonyl compounds. Although the reaction was slow (three days), the reaction of 10-undecen-l-ol (50) with iodobenzene afforded the aldehyde 52 in a high yield. In this... 

Aryl radical cyclization.10 Sml2 in HMPA/THF at 25° can effect cyclization of l-allyloxy-2-iodobenzene to a Sm(III) intermediate (a) that can be trapped by electrophiles, including aldehydes or ketones. The report suggests that a similar mechanism operates in the Barbier-type coupling generation of an alkyl radical followed by formation of RSml2, which adds to a carbonyl compound to form an adduct that is hydrolyzed to an alcohol. 

Benzyl halides have been reported to react with nickel carbonyl to give both coupling and carbonylation (59). Carbonylation is the principal reaction in polar nonaromatic solvents, giving ethyl phenylacetate in ethanol, and bibenzyl ketone in DMF. The reaction course is probably similar to that of allylic halides. Pentafluorophenyl iodide gives a mixture of coupled product and decafluorobenzophenone. A radical mechanism has been proposed (60). Aromatic iodides are readily carbonylated by nickel carbonyl to give esters in alcoholic solvents or diketones in ethereal solvent (57). Mixtures of carbon monoxide and acetylene react less readily with iodobenzene, and it is only at 320° C and 30 atm pressure that a high yield of benzoyl propionate can be obtained (61). Under the reaction conditions used, the... 

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. 

However, for other palladium catalysed reactions of organozinc iodides with electrophiles, THF is a good choice of solvent. The incompatibility of THF and acid chlorides at ambient temperature can also be overcome, in some cases, by the use of a carbonylative cross-coupling in which an iodobenzene derivative is used as the precursor.17... 

The asymmetry parameters of substituted chlorobenzenes and iodobenzenes have been discussed above in Section III.A.3 (Tables 4 and 5). The asymmetry parameters of several systems are discussed below carbonyl chlorides in Section III.B.4, a variety of substituted vinyl chlorides in Section III.B.9 and methylene dichloride and chloroform in Section III.B.lO.c. There remain a number of measurements of asymmetry parameters30-33, mainly of aliphatic systems, that are not covered elsewhere and these are listed in Table 7. It will be seen that the asymmetry parameters of chlorine atoms bonded to saturated carbon atoms are always small, of the order of 0.05 or less, while if the chlorine atom is bonded to an sp2-hybridized carbon atom then the asymmetry parameter is generally equal to or greater than 0.1. 

Metallated 1-ethoxy-1,3-dienes 697 and 712, obtained from the corresponding acetals by means of the LICKOR base, have been treated with alkyl halides, epoxides, carbonyl compounds, carbon dioxide and carboxylic esters affording ( )-l-substituted 1-ethoxy-1,3-dienes and, after hydrolysis, a,P-unsaturated carbonyl compounds1007-1010 (Scheme 186). Intermediates 697 and 712 have been transformed into the corresponding vinyl stan-nanes, which were submitted to Stille couplings with iodobenzene and benzoyl chloride823. 

The same reaction was also investigated using the palladium-carbene complex, 58, as catalyst (Scheme 9.12).1401 Of the different ionic liquids studied, tetrabutylammonium bromide gave by far the best results while imidazolium based solvents afforded only poor conversions. At atmospheric pressure, only iodobenzene was carbonylated. The conversion of less reactive arylhalides not only required higher CO-pressures, but also the addition of a phosphine ligand. Reuse of the catalyst after extraction of the product with diethyl ether was possible for at least 6 runs with only a moderate decrease in activity. 

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