Carbonyl halides, reactions

Halide-carbonyl reactions. The intramolecular reaction of an allylic chloride with... 

The proton of terminal acetylenes is acidic (pKa= 25), thus they can be deprotonated to give acetylide anions which can undergo substitution reactions with alkyl halides, carbonyls, epoxides, etc. to give other acetylenes. 

Addition to Carbonyl Compounds. Unlike Grignard and alkykitliium compounds, trialkylboranes are inert to carbonyl compounds. The air-catalyzed addition to formaldehyde is exceptional (373). Alkylborates are more reactive and can transfer alkyl groups to acyl halides. The reaction provides a highly chemoselective method for the synthesis of ketones (374). 

This method ensures the deposition of very reactive metal nanoparticles that require no activation steps before use. We shall review here the following examples of catalytic reactions that are of interest in line chemical synthesis (a) the hydrogenation of substituted arenes, (b) the selective hydrogenation of a, 3-unsaturated carbonyl compounds, (c) the arylation of alkenes with aryl halides (Heck reaction). The efficiency and selectivity of commercial catalysts and of differently prepared nanosized metal systems will be compared. 

Coupling of organostannanes with halides in a carbon monoxide atmosphere leads to ketones by incorporation of a carbonylation step.249 The catalytic cycle is similar to that involved in the coupling of alkyl or aryl halides. These reactions involve Reactions involving a migration of one of the organic substituents to the carbonyl carbon, followed by... 

Application of the carbonylation reaction to halides with appropriately placed hydroxy groups leads to lactone formation. In this case the acylpalladium intermediate is trapped intramolecularly. 

The palladium-catalyzed Heck carbonylation reaction is a powerful means of generating amides, esters, and carboxylic acids from aryl halides or pseudohalides [28]. The development of rapid, reliable, and convenient procedures for the introduction of carbonyl groups is important for the development of high throughput chemistry in general and high-speed microwave-mediated chemistry in particular. Unfortunately, the traditional method of introducing carbon monoxide into a reaction mixture via a balloon or gas tube is not practical because of the special requirements of microwave synthesis. 

Analogous carbonylation reactions using nickel and iron carbonyl based systems also produce alkanecarboxylic acids [11, 13, 14]. The mechanism of the conversion of benzyl halides into arylacetic acids using iron pentacarbonyl is not as well defined as it is for reactions promoted by nickel or molybdenum carbonyl complexes. Iron... 

When sodium ethoxide is used in place of sodium hydroxide in the carbonylation reaction of benzyl halides with dicobalt octacarbonyl, ethyl esters are produced instead of the acids [15], Esters are also produced directly from iodoalkanes through their reaction with molybdenum hexacarbonyl in the presence of tetra-/i-butylammo-nium fluoride [16]. Di-iodoalkanes produce lactones [16]. The reaction can be made catalytic in the hexacarbonyl by the addition of methyl formate [16]. t-Butyl arylacetic esters are produced in moderate yield (40-60%) under phase-transfer catalytic conditions in the palladium promoted carbonylation reaction with benzyl chlorides [17]. 

Complexes of other metals are also capable of catalyzing useful carbonylation reactions under phase transfer conditions. For example, certain palladium(o) catalysts, like Co2(C0)g, can catalyze the carbonylation of benzylic halides to carboxylic acids. When applied to vinylic dibromides, unsaturated diacids or diynes were obtained, using Pd(diphos)2[diphos l,2-bis(diphenylphosphino)ethane] as the metal catalyst, benzyltriethylammonium chloride as the phase transfer agent, and t-amyl alcohol or benzene as the organic phase(18),... 

It has been shown very recently that carbonylation reactions can also be performed by electrolyzing under CO a solution of organic halide containing... 

The same research group has further performed radical carbonylation reactions on the same microreactor system [36]. First, alkyl halides were initiated and effectively reacted with pressurized carbon monoxide to form carbonyl compounds. The principle was subsequently successfully extrapolated to the multicomponent coupling reactions. 1-Iodooctane, carbon monoxide and methyl vinyl ketone were reacted in the presence of 2,2 -azobis(2,4-dimethylvaleronitrile) (V-65) as an initiator and tributyltin hydride or tris(trimethylsilyl)silane (TTMSS) as catalyst (Scheme 15). 

NMR spectra, 20 347 structural parameters, 20 297, 299 structure of, 20 300 chalcogenide halides, 23 381-382 structure, 23 382 complexes, 6 2 anation reactions, 34 225 with bipy and phen, 12 185-187 5-coordinate, 34 229, 234, 236-238 with divalent tin, 11 119 with germanium, 11 107-108, 112 homoleptic, 2,2 -bipyridine, 34 28-30 with olefins, 12 311-316 sulfoxides, 24 166 carbonylation reactions, 24 143 and catalyzed decomposition of H2O2, 24 150-151... 

The picture is different for the bimetallic ruthenium-rhodium systems both metals in the presence of iodide promoters and CO give anionic iodocarbonyl species, namely [Ru(C0) I ] and [Rh(CO)2l2] j but the range of I, CO concentration and temperature in which the anions exist and are catalytically active in carbonylation reactions is different. [Ru(CO)3l2] species in fact are extensively transformed at high temperature and low carbon monoxide pressure by an excess of I (i.e. I/Ru 50) into catalytically inactive [Ru(CO)2l4] (v q 2047, 1990 cm"l in THF (JJ.)) (eq. 1), whereas [Rh(CO)2l2] can work in the carbonylation process only in the presence of a large excess of I"" (I/Rh 100-1000) which prevents reduction to metal (12) (for instance at 150 C rhodium(I) carbonyl halides, [Rh(CO) X2]"", without CH3I under a CO/H2 pressure of 10 MPa are completely reduced to metal). 

Since Wakamatsu serendipitously discovered amidocarbonylation while performing the cobalt-catalyzed hydroformyla-tion of olefins in 1971, this unique carbonylation reaction, affording a-amino acids directly from aldehydes, has been extensively studied.More recently, palladium-catalyzed processes have been developed to expand the scope of this reaction.The Pd-catalyzed amidocarbonylation has been applied to aldehydes,aryl halides, and imines. As a related reaction, lactamization " of aryl halides catalyzed by a rhodium complex has also been developed. 

Radical carbonylation reaction serves as a powerful tool for the synthesis of a range of carbonyl compounds. Radical carbonylation has been successfully applied to the synthesis of functionalized ketones from alkyl, aryl, and alkenyl halides.The radical aminocarbonylation reaction of alkynes and azaenynes provided efficient routes to 2-substituted acrylamides, lactams, and pyrrolidinones. For example, the aminocarbonylation of 4-pentyn-l-yl acetate 318 initiated by tributyltin hydride (Bu"3SnH) (30mol%) with AIBN (20mol%) gave acrylamide 325 in 92% yield (Scheme 43).A proposed mechanism starts from the addition of tributyltin radical 319 to alkyne... 

Moreover, reaction time was reduced from hours to minutes or even seconds. Indeed, the carbonylation of aryl halides 335 was completed in 10 s to give symmetrical diaryl ketones 336 in excellent yields (Equation (31)). The process optimization to reduce the amount of catalyst disclosed the fact that this carbonylation reaction followed a radical pathway, initiated by the homolytic cleavage of Co2(CO)8 into -00(00)4. It also appeared that the amount of the Oo catalyst had a direct correlation with the internal temperature reached during the reaction. These findings are critical for the development of extremely fast synthesis using carbonylations. 

A very versatile preparation seems to be the elimination of organotin halides in the reaction of organostannyl-organosilylcyclopentadienes with metal carbonyl halides. This reaction is very selective and only Sn—C bonds are cleaved with formation of 7)5-cyclopentadienyl complexes (7) ... 

Carbonylation of Halides - Pd(tppts)3-catalysed carbonylation of bromo-benzene (Equation 7) in the presence of NEt3 in an aqueous/toluene (1/1) two phase system at 150°C and 15 bar CO afforded the triethylammonium salt of benzoic acid (100% yield).464,465 Rates were rather low (TOF s of 3.3-17 h ) but no decomposition of Pd(tppts)3 (tppts/Pd 12.5) was observed and the catalyst could be recovered quantitatively and recycled 464 However, in a second recycle extensive decomposition of the catalyst occurred with formation of palladium black. Generally in carbonylation reactions of halides the formation of stoichiometric amounts of either HX or halide salts still remains a problem of environmental concern despite the attractiveness due to the presence of the aqueous solvent. 

Fluoride complexes of organometallics can be readily prepared by halide abstraction reactions. The general reaction scheme for a carbonyl species ... 

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