Organocatalytic selective benzoylation of alcohols with trichloromethyl phenyl ketone: inverse selectivity in benzoylation of alcohols containing phenol or aromatic amine functionality

Practical Chemoselective Acylation: Organocatalytic Chemodivergent Esterification and Amidation of Amino Alcohols with N‐Carbonylimidazoles

“…[23] Neither steric (9,14)n or electronic effects (12,13)f rom the acyl group significantly affected selectivity or yield. Similarly,imidazole carbamates could be employed in achemoselective synthesis of carbonates (16,17). Imidazole ureas (18)could also be used to produce carbamate products,a lbeit with noticeably reduced reaction rates relative to other carbonylimidazole electrophiles.…”

“…Enzyme‐catalyzed esterification reactions of amino alcohols have been reported, for instance of a Phe‐Ser dipeptide with a lipase, [15] as have several other niche methods. For instance, alcohols may be esterified in the presence of anilines by a modified haloform reaction [16] and sufficiently electron‐poor anilines can act as spectators in carbodiimide‐mediated esterification [17] and Mitsunobu reactions [18] …”

“…Selective esterification of amino alcohols may also be achieved with N-heterocyclic carbene (NHC) catalysis of oxidative esterification [13] or transesterification. [14] Enzymecatalyzed esterification reactions of amino alcohols have been reported, for instance of aPhe-Ser dipeptide with alipase, [15] as have several other niche methods.F or instance,a lcohols may be esterified in the presence of anilines by am odified haloform reaction [16] and sufficiently electron-poor anilines can act as spectators in carbodiimide-mediated esterification [17] and Mitsunobu reactions. [18] However,i no rder to achieve these more challenging chemoselectivities,p ractical considerations,s uch as scope, cost, or reagent availability,a re often sacrificed-a fundamental tension in the development of new synthetic methods.…”

Highly selective acylation of polyamines and aminoglycosides by 5-acyl-5-phenyl-1,5-dihydro-4H-pyrazol-4-ones

“… 3 Over the years numerous acyl transfer agents have been investigated; their activities have been dependent on the leaving group, which has ranged from those of the highly reactive acyl chlorides and anhydrides to those that are conjugate bases of relatively weak acids. The linkage to the acyl group has included N -imidazolyl 4a – g and N -benzotriazolyl, 4h – m succinimidyloxy, 5 cyanide, 6 sulfonamide, 7 trichloromethyl, 8 enolates, 9 and, most recently, boron trifluoride. 10 Selectivity in acyl transfer has become an important goal with achievements evolving beyond chemoselection (OH vs. SH vs. NH acylation) 11 to selective acylation of primary amines over secondary amines.…”

“…This compound, 5-benzoyl-3-(cyclopent-1-en-1-yl)-5-phenyl-1,5-dihydro-4 H -pyrazol-4-one (BCPP, 1a ), which is formed in one step from a propargyl phenyldiazoacetate by gold( i ) catalysis, 16 has its benzoyl group attached to carbon-5 of a pyrazolone ring so that the conjugate base of hydroxypyrazole is the leaving group ( Scheme 1 ). Acyl transfer reagents that, like BCPP, have carbon-linked leaving groups, principally cyano, 6 , 14a trichloromethyl, 8 2-imidazolyl, 11f , 17 among a few others, 14d , 18 generally exhibit higher chemoselectivities than their heteroatom-linked counterparts. However, to our knowledge, acylating agents whose leaving group undergoes aromatization upon acyl transfer (transformation of 1 to 4 , Scheme 1 ) have not been reported.…”