Carbonyl migration

Reaction of etio acid 67 with N,N-dimethylthioformamidoyl chloride probably gives initially the mixed anhydride 71 this is not isolated but undergoes O to S carbonyl migration to the anhydride 72. Saponification then leads to the thioacid 73. Reaction of the sodium salt of the acid witli bromochloromethane affords cloticasone propionate (74). The corresponding reaction with hioniofluoromethane leads to fluticasone propionate (75) [16]. 

Ligand fluxionality on metal clusters has been the subject of many studies, the majority of reports focusing on carbonyl migration on homometallic tri- and... 

The steps in the hydroformylation reaction are closely related to those that occur in the Fischer-Tropsch process, which is the reductive conversion of carbon monoxide to alkanes and occurs by a repetitive series of carbonylation, migration, and reduction... 

This reaction is kinetically favored because the oxygen of water is a nucleophile, whereas the carbonyl carbon is an electrophile. In the initial step the curved, colored arrows that represent the flow of electron pairs suggest three electron pair migrations that happen in quick succession (figure 10a). An electron pair migrates from the O—H of the water molecule to the O. An electron pair from the O attacks the carbonyl carbon, and an electron pair between the C and the O in the carbonyl migrates to the O of the carbonyl. The intermediate step involves the results of these and two additional electron pair migrations from the relatively unstable intermediate products that lead to the final products. 

Compound 740, when heated, undergoes 6, A -carbonyl migration and subsequent cyclization to afford thiolactone 741 (Scheme 115) <2004CEJ6102>. 

The o-lithio intermediates undergo an unexpected O — C 1,3-carbonyl migration to salicylamides at 25°. This migration is an equivalent of the Fries rearrangement. Example ... 

The principle of microscopic reversibility requires that any reversible reaction must have identical pathways for the forward and reverse reactions, simply proceeding in opposite directions. (This principle is similar to the idea that the lowest pathway over a mountain chain must be the same regardless of the direction of travel.) If the forward reaction is carbonyl migration (Mechanism 2), the reverse reaction must proceed by loss of a CO ligand, followed by migration of CO from the acyl ligand to the empty site. Because this migration is unlikely to occur to a trans position, all the product should be... 

In addition to the normal photochemical reactions of saturated ketones, p,y-unsaturated carbonyl compounds undergo carbonyl migration via a [1,3] shift. Compound 139 in Scheme 45 represents a typical example. Compounds with an alkyl substituent in the P position such as 140 may also undergo a Norrish type II reaction (Kiefer and Carlson, I%7), while for ketones with electron-rich double bonds such as 141, oxetane formation is also observed (Schexnayder and Engel, 1975). 

The dichloromethane solution of 63 was directly subjected to amidation by the use of the Katritzky s protocol [86] using H2O2 and K2CO3 in DMSO (Fig. (30)). The reaction smoo ly proceeded even in a mixed solvent of DMSO and CH2CI2 to afford the corresponding amide 64, a substrate for the 5,iV-carbonyl migration. The. sy/r-isomer sy -64 was obtained as a solid in 93% yield by just adding water to the reaction... 

Upon heating the Jv -amide syn-64 up to 90 C in DMF under nitrogen atmosphere, j jA -carbonyl migration started and was completed in 1 h to provide thiol amide 74 (Fig. (31)), The resulting solution involving 74... 

In the case of the a t/-isomer hydrochloride, i //-64 HCl, when heated at a higher temperature (120°C) for 5 h under nitrogen atmosphere, the S, A/ -carbonyl migration took place to directly give thiolactone 8 in 91% yield (Figure (32)),... 

The intermediacy of free radicals in the autoxidation and peroxide-catalyzed processes was established by CIDNP observations. The rate constant for carbonyl migration, i.e. for... 

In this reaction, y ionone is converted into its oxime 19 which is oxidized to the isoxazole 20 by a special method (reaction with KJ and NaHC03 in THF/water). The compound 20 is converted into y damascenone by use of sodium in liquid ammonia in the presence of er/-butanol without isolation of the intermediate y amino ketone 21 yield 72% (based on y ionone). In this reaction, the heterocycle facilitates a 1,3-carbonyl migration within an a,y0-unsaturated carbonyl system. 

The carhonylation from cA-MnCH3( CO)(CO)4 gave the acyl products, whose positional ratios of isotopic label on the basis of C NMR were compatible with the methyl migration mechanism [18]. The mixture of the Mn( COCH3)(CO), cis, and tra 5-CH3COMn( CO) products (see Scheme 7.3) was obtained in a ratio of 1 2 1, whereas the carbonyl migration pathway would not have provided the trans isomer. 

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