Diaryl ketone urea

R-Y-COCl plays the key role in phosgenation reactions that are of a stepwise nature the major part of these processes is COCl (chlorocarbonyl) transfer to R-Y-H generating chloroformates, carbamoyl chlorides, etc. R-Y-COCl is of limited (low) stability and this is the driving force behind its intermediacy in the synthesis of chlorides and isocyanates under elimination conditions (eliminating CO2 and/or HCl), and also determines the character of a reactive substrate in further nucleophilic substitutions to form symmetrical and unsymmetrical substituted carbonic acid derivatives carbonates, carbamates, ureas) or diaryl ketones. Commonly, chloro-formylation and isocyanate formation are independent of the nature of R. Obviously, the reactivity is very different due to the relative basic/nucleophilic ratio. For example, Ar-Cl cannot be prepared through a chloroformate intermediate nor by direct phosgenation, but the reaction does work well in the aliphatic series. 

In a related three-component reaction procedure, aryl methyl ketones 724 have been combined with aryl aldehydes 725 and urea 726 at room temperature, using trimethylsilyl iodide as catalyst, to give 4,6-diaryl-3,4-dihydro-2(177)-pyrimidinones 727 <2005HCA2996>. A procedure using zinc iodide and microwave irradiation gave similar products <2007T1981>. 

The Beckmann rearrangement of ketoximes to the corresponding amides (31), the Fischer indole cyclization, isomerization of epoxides to the corresponding aldehydes, ketones, or alcohols, hydration and ammo-nolysis of epoxides, oxygen-sulfur interchange, formation of diaryl-ureas and -thioureas from condensation of aniline and carbonyl sulfide, and olefin carbonylation occur over zeolite catalysts (62). The oxo reaction over rhodium and cobalt containing zeolites recently has been claimed (22). 

Transition metals can be eliminated from the catalytic systems. Thus, a quinine-derived urea organocatalyst is effective in the enantioselective oxidation of a wide range of diaryl-substituted meso-1,2-diols using bromi-nation reagents as oxidants (Scheme 31). " The method is simple, operates at ambient temperature and utilizes available reagents to yield a-hydroxy ketones in good yields (up to 94%) and enantioselectivities (up to 95% ee). 

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