Carbon monoxide equivalent

The preparation of the C1-C21 subunit of the protein phosphatase inhibitor tautomycin was completed by J.A. Marshall et al., and it constituted a formal total synthesis of the natural product. The spiroketal carbon of the target was introduced by the Weinreb ketone synthesis between a lithioalkyne and A/-methoxy-A/-methylurea (a carbon monoxide equivalent). The triple bond of the resulting Weinreb s amide was first reduced under catalytic hydrogenation conditions to yield the corresponding saturated amide, which was reacted with another lithium acetylide to afford an ynone. 

For a review of carbonylation reactions using carbon monoxide equivalents, see [119]. For selected examples, see [122-124]. 

By passing a mixture of carbon monoxide and hydrogen chloride into the aromatic hydrocarbon in the presence of a mixture of cuprous chloride and aluminium chloride which acts as a catalyst (Gattermann - Koch reaction). The mixture of gases probably reacts as the equivalent of the unisolated acid chloride of formic acid (formyl chloride) ... 

According to Faraday s law, one Faraday (26.80 Ah) should deposit one gram equivalent (8.994 g) of aluminum. In practice only 85—95% of this amount is obtained. Loss of Faraday efficiency is caused mainly by reduced species ( Al, Na, or A1F) dissolving or dispersing in the electrolyte (bath) at the cathode and being transported toward the anode where these species are reoxidized by carbon dioxide forming carbon monoxide and metal oxide, which then dissolves in the electrolyte. Certain bath additives, particularly aluminum fluoride, lower the content of reduced species in the electrolyte and thereby improve current efficiency. 

Lithium 1,2,4-triazolate with [Rh2( j,-Ph2PCH2PPh2)(CO)2( j.-Cl)]PFj. gives the A-framed complex 177 (L=L = CO) (86IC4597). With one equivalent of terf-butyl isocyanide, substitution of one carbon monoxide ligand takes place to yield 177 (L = CO, L = r-BuNC), whereas two equivalents of rerr-butyl isocyanide lead to the product of complete substitution, 177 (L = L = r-BuNC). The starting complex (L = L = CO) oxidatively adds molecular iodine to give the rhodium(II)-rhodium(II) cationic species 178. 

H), followed by bromine-lithium exchange using 2 equivalents of tert-butyllithium to give the desired intermediate. This intermediate readily picked up carbon monoxide and work-up of the reaction mixture gave indigo (Fig. 17) (ref. 31). 

Various l-alkyl-4-(benzotriazol-l-yl)-l,2,3,4-tetrahydroquinolines have been prepared by condensation of V-alkylaniline with two equivalents of an aldehyde and one equivalent of benzotriazole <95JOC(60)7631>. Quinolones 66 were simply prepared in good yield by heating a mixture of the appropriate vinylogous amide 65 and NaHCOj in the presence of a catalytic amount of palladium(II) acetate and triphenylphosphine in DMF under a carbon monoxide atmosphere <96CC2253>. 

Similarly, Pd/tppts was used by Hoechst (Kohlpainter and Beller, 1997) as the catalyst in the synthesis of phenylacetic acid by biphasic carbonylation of benzyl chloride (Fig. 2.29). The new process replaces a classical synthesis by reaction of benzyl chloride with sodium cyanide, followed by hydrolysis of the resulting benzyl cyanide. Although the new process produces one equivalent of sodium chloride, this is substantially less salt production than in the original process. Moreover, sodium cyanide is about seven times as expensive per kg as carbon monoxide. 

The [2+2+1] cycloaddition of an alkene, an alkyne, and carbon monoxide is known as the Pauson-Khand reaction and is often the method of choice for the preparation of complex cyclopentenones [155]. Groth and coworkers have demonstrated that Pauson-Khand reactions can be carried out very efficiently under microwave heating conditions (Scheme 6.75 a) [156]. Taking advantage of sealed-vessel technology, 20 mol% of dicobalt octacarbonyl was found to be sufficient to drive all of the studied Pauson-Khand reactions to completion, without the need for additional carbon monoxide. The carefully optimized reaction conditions utilized 1.2 equivalents of... 

Th[(0113)505] 2Cn -C0CH2C(CH3)3]C1 reacts with an additional equivalent of carbon monoxide according to eq.(3). 

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