Dialkyls with carbon monoxide

Bercaw and coworkers have studied the reaction of bis(penta-methylcyclopentadienyl)zirconium dialkyls with carbon monoxide (47,48). As in the case of the aforementioned biscyclopentadi-enyls, reversible monoinsertion is observed (equation (7)) yielding a bihaptoacyl (vqq 1537 cm"1). Interestingly, when car-... 

Thermal or photo-induced decompositions of dialkyl peroxides in the presence of suitable substrates yield various products. For example, with nitric oxides, alkyl nitrites or nitrates are formed and, with carbon monoxide, Z fZ-alkyl esters are obtained (44) ... 

As mentioned in the preceding section, the presence of water during the reaction of trialkylboranes with carbon monoxide inhibits the migration of the third alkyl group and leads to production of dialkyl ketones (i). This fact can be employed to advantage for the preparation of dialkyl ketones as shown in the scheme. 

Reaction of dialkyl derivatives of zirconium(IV) of formula Zr(j -C5Me5)2R2 with carbon monoxide gives a mononuclear ene-diolato compound resulting from carbon-carbon coupling of the product of monoinsertion into both zirconium-carbon bonds ... 

Preparation of dialkyl 1-formylethylphosphonates can be achieved in low to good yields (27-71%) by reacting dialkyl vinylphosphonates with carbon monoxide and hydrogen (1/1 CO/H2 ratio) in the presence of a conventional rhodium-containing hydroformylation catalyst [Rh(COD)Cl]2 at temperatures ranging from 60°C to 130 C under a pressure of 20-1500 bars (Scheme 5.15). Hydroformylation can be carried out with or without solvent. Loading of rhodium catalyst from 0.5 to 500 ppm have proved suitable. 

The reaction is sensitive to the presence of water, which inhibits the migration of the third alkyl group and leads to dialkyl ketones (see Chapter 12, Section II). The convenience of the hydroboration reaction combined with the use of carbon monoxide at atmospheric pressure provides the most accessible route to many trialkylcarbinols. 

The following dialkyl ketones may be prepared by an analogous procedure with the time required for the absorption of carbon monoxide as shown (Table 12.2). 

Carbon monoxide rapidly inserts into the carbon—zirconium bond of alkyl- and alkenyl-zirconocene chlorides at low temperature with retention of configuration at carbon to give acylzirconocene chlorides 17 (Scheme 3.5). Acylzirconocene chlorides have found utility in synthesis, as described elsewhere in this volume [17]. Lewis acid catalyzed additions to enones, aldehydes, and imines, yielding a-keto allylic alcohols, a-hydroxy ketones, and a-amino ketones, respectively [18], and palladium-catalyzed addition to alkyl/aryl halides and a,[5-ynones [19] are examples. The acyl complex 18 formed by the insertion of carbon monoxide into dialkyl, alkylaryl, or diaryl zirconocenes may rearrange to a r 2-ketone complex 19 either thermally (particularly when R1 = R2 = Ph) or on addition of a Lewis acid [5,20,21]. The rearrangement proceeds through the less stable... 

The complexes of borane (BH3) itself with amines, phosphines, dialkyl sulfides and carbon monoxide, the first representatives prepared only in die 1930s were thoroughly discussed in several books and reviews.2,9,25-36 Therefore, in this section, only a brief summary will be given outlining the most basic aspects of these compounds, whereas complexes of substituted boranes will be discussed in more detail. 

Diisopropyl Malonate. This dialkyl malonate has gained industrial importance lor the synthesis of the fungicide isoprolhiolnne through condensation with carbon disulfide and ethylene dichloride. Diisopropyl malonate is produced b> Miisuhishi Chemical (Japan) using the carbon monoxide process. 

Aromatic urethanes and dialkyl carbonates were simultaneously prepared by the reaction of aromatic nitro compounds with alcohols and carbon monoxide over a catalyst mixture containing DBU (82JAP(K)32251). 

Carbon monoxide insertion into the copper-alkyl bond is indirectly shown by reaction of CO with dibutylcuprate(I), an anionic dialkyl derivative of dicoordinated copper(I). The product of the reaction, dibutylketone, may be rationalized by assuming carbon monoxide coordination to the anionic copper complex, followed by alkyl migration to the unstable anionic complex Cu[C(0)Bu](Bu) , with subsequent reductive elimination to the observed organic product. 

The possibility that olefin-carbon monoxide copolymers can exist in the isomeric poly-spiro ketal structure (Scheme 8.5) was recognized soon after the first synthesis of the copolymers of propene. Using dialkyl diphosphines as the modifying ligands [27], copolymers were obtained with blocks with the spiroketal form [28]. 

The anions generated from tetracarbonyl(phosphine) carbene complexes are more reactive in their reactions with organic electrophiles. This is consistent with the observation that the pATa of the methyl pentacarbonyl complex (88a) is increased by six orders of magnitude when one of the carbon monoxide ligands is replaced with tributylphosphine. The anion generated from (106) will give good yields of alkylated products with simple alkyl halides such as ethyl bromide however, dialkylation is still a serious side reaction. It has been reported that both pentacarbonyl and tetracarbonyl(phosphine) complexes can be efficiently monoalkylated with alkyl triflates (primary and secondary). The anion (89) for example, can be monoalkyated with the 3-butenyl triflate in 80% yield. ... 

Tandem sequences have also yielded some interesting pyrazole structures. Four-component coupling of terminal alkynes 37, hydrazines 38, carbon monoxide and aryl iodides furnished pyrazoles 39 in the presence of palladium catalyst <05OL4487>. Fully substituted 1/f-pyrazoles 42 were prepared from the condensation/fragmentation/cyclization/extrusion reactions of thietanone 40 with 1,2,4,5-tetrazines 41 <05JOC8468>. Reactions of isocyanides 43 and dialkyl acetylenedicarboxylates 44 in the presence of 1,2-diacylhydrazines 45 led to highly-functionalized pyrazolines 46 <05TL6545>. 

N,N-Dialkylation of primary amines. Primary amines can be dialkylated by the reaction with an aldehyde and potassium hydridotetracarbonylferrate in ethanol under carbon monoxide at 20. ... 

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