2-Phenyl-2-oxazolin-5-ones, alkylation

The bidentate oxazoline ligands 85 and 86 (and derivatives thereof) are excellent reporter ligands, and several studies have used NOEs to determine the nature of their chiral pockets [61, 113, 114, 126]. NOESY studies on the cations [Ir(l,5-COD)(86)]+ and several cationic tri-nudear Ir(iii)(hydrido) compounds [110], e. g. [Ir3(p3-H)(H)5(86)3] +, 87, in connection with their hydrogenation activity, allowed their 3-D solution structures to be determined. In addition to the ortho P-phenyl protons, the protons of the oxazoline alkyl group are helpful in assigning the 3-D structure of both the catalyst precursors and the inactive tri-nudear dusters. Specifically, for one of these tri-nudear Ir(iii) complexes, 87 [110], with terminal hydride ligands at d -17.84 and d -21.32 (and a triply bridging hydride at 5 -7.07), the P-phenyl and oxazoline reporters define their relative positions, as shown in Scheme 1.5. 

The requisite 2-aryl-2-oxazolin-4-ones can be synthesized using the procedure briefly described by Gordon for the preparation of 2-phenyl-2-oxazolin-4-one (65a)53K The method utilizes an intramolecular O-alkylation of an imide ambident anion. 

Phenyl-2-oxazolin-5-one undergoes ready 4,4-substitution with activated alkyl halides. " Oxidation of the a,a-dialkylated hippuric acids obtained from hydrolysis of the oxazolinones then yields symmetrical ketones (Scheme 17). 

Oxazolin-4-ones, 106 2-Oxazolin-6-ones, acyl donors, 82 acylamino ketones from, 82 acylation of, 82-86 4-alkyl-, oxidative coupling of, 80 in amino acid syntheses, 89-91 4-arylidene-, ring-opening of, 93 4-arylidene-2-phenyl-, 95 azidolysis of, 81 4-benzylidene-2-styryl-, 93 hia derivatives of, 79-81 conversion into other heteroc3 1es, 91-92... 

Scheme 1 shows the "One-pot Two-stage" process to produce AB type block copolymer, in which the first monomer is MeOZO and the second one is a 2-oxazoline derivative having a medium to higher alkyl or phenyl group. 

The action of 2-phenyl-A -oxazolin-5-one (141) on 2-alkyl-A -thiazolines (142) proceeds by the nucleophilic attack on C-2 of the latter. Subsequent fission of the thiadiazolidine ring of the presumed intermediate (143) occurs at either the 1,2- or 2,3-bond, yielding the two products (144) and (145) side by side. The compounds (144) are obtained exclusively, in high yield, when the reaction is performed in pyridine at room temperature. 

---