Chemoselective functionalization ketone

Organomanganese reagents have also been used to prepare numerous simple or functionalized ketones in high yields.10 They can be also used to carry out in high yields, at room temperature, various chemoselective 1,2-addition reactions, for example to keto aldehydes.11... 

Potassium triisopropoxyborohydride, a mild selective reducing agent, rapidly converted ketones and aldehydes to the corresponding alcohols, while many common functional groups were inert.The reaction of potassium hydride with triphenylborane produced the triphenylborohydride, which is highly hindered and which exhibited excellent chemoselectivity between ketones. Cyclohexanone was reduced in preference to cyclopentanone (97 3) and 4-heptanone (99.4 0.6), while methyl ketones were more reactive than 4-heptanone (2-heptanone, 94 6 acetophenone, 97.8 2.2). 

A few examples of chemoselective additions of allyltitanium reagents to aliphatic and aromatic carbonyl compounds are reported in Table 7. Appreciable chemoselectivity toward the aldehydic function is achieved by the titanium ate conqtlex (23), whereas the reverse chemoselectivity toward ketones is realized using aminotitanium complex (104) and the analogous ate complexes (24) and (25), as is shown in Table 7. This is very interestii since it represents a rare case of chemoselectivity in favor of carbanion addition to ketones. A tentative explanation of this inverse chemoselection considers a fast transfer of the aminyl ligand onto the aldehyde function which becomes protected , as in (105), and thus unreactive in respect to the keto group. Ketones react also selectively compared with esters, as is shown by the reaction of ethyl levulinate (1) with the ate complex (23 equation 40). ... 

MAPH is another possibility available for the chemoselective functionalization of ketones (Scheme 2-12) [12]. The alkylation involved in mode F3 is almost inoperative because the aldehydic carbon is steiically, i.e., kinetically, deactivated by the cooperation of the MAPH ligands, thereby presumably forming a sort of sandwich stmcture (1-4). The reaction rate of RLi (R Bu, Ph, etc.) with ketones consequently becomes faster. 

In 2013, Law and McErlean demonstrated the intramolecular vinylogous Stetter reaction as a new addition to the collection of NHC-catalyzed transformations. The products of this new transformation possess multiple sites for chemoselective functionalization, including (but not limited to) ketones, esters, and alkenes. Utilizing chiral triazolium salts as the NHC catalyst precursor, aromatic aldehydes or aliphatic aldehydes proceeded with various heteroatom tethered vinylogous Michael acceptors to give five- and sk-membered rings (up to 88% yield, 96% ee) (Scheme 7.20). 

Huonnations with DAST proceed with high chemoselectivity In general, under very mild reaction conditions usually required for the replacement of hydroxyl groups, other functional groups, including phenolic hydroxyl groups [112], remain intact This provides a method for selective conversion of hydroxy esters [95 97] (Table 6), hydroxy ketones [120, 121], hydroxy lactones [722, 123], hydroxy lactams [124] and hydroxy nitriles [725] into fluoro esters, fluoro ketones, fluoro lactones, fluoro lactams, and fluoro nitnles, respectively (equations 60-63)... 

Alkylation of organomanganese reagents with alkyl bromides can also be improved by addition of CuCI (3 mol%). The reactions proceed at room temperature and are complete within a few hours [123, 130], The opening of epoxides is also improved under these conditions. The reaction also features good chemoselectivity, tolerating the presence of sensitive functions such as ketones (Scheme 2.59) [130]. 

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