4-bis oxazolones

Dimerization can also be achieved using nickel peroxide " or through a photooxidation reaction. In these cases, 4-monosubstituted-5(4//)-oxazolones 293 are converted to the corresponding 4,4 -bis(oxazolones) 294 (Scheme 7.97 ... 

TABLE 7.26. 4,4 -BIS(OXAZOLONES) FROM DIMERIZATION OF SATURATED 5(477)-OXAZOEONES... 

Reaction of carbon disulfide with 2-phenyl-5(4//)-oxazolone 146 followed by S-alkylation with a methyl hahde gives 4-[bis(methylthio)methylene]-2-phenyl-5(4//)-oxazolone. The solvolysis and aminolysis of this compound have also been studied. ... 

The second group of saturated 5(47/)-oxazolones used as intermediates for polymer synthesis are the 2,2 -bis(oxazolones) with 2,2 -bis[4,4-dimethyl-5(47/)-oxazolone] 329 being the simplest member of the series (Fig. 7.33). These compounds, are prepared by cyclization of the corresponding bis(amino acids) and give a wide variety of polymers after ring opening with diamines, dialcohols or other nucleophiles. The physical chemical properties of these polymers depend on the nature of the substituents and the size of the chain. Some selected references describe representative examples. 

If the anion of 2-(2 -hydroxyphenyl)-5(4/l/)-oxazolone 336 is used as a ligand, bis-chelate complexes 337 of copper(II), nickel(II), and zinc(II) have been prepared from the corresponding metal acetates. Alternatively, 336 and 2-(2 -aminophenyl)-5(4//)-oxazolone 340 can act as ligands with metals including palladium(II), platinum(II), ruthenium(II), nickel(II), and copper(II) to produce a variety of structurally diverse complexes 338, 339, and 341 as shown in Schemes 7.109 and 7.110. ° ... 

Heteromethylene-5(4//)-oxazolones 439 show similar behavior to that described above. Hydrolysis or alcoholysis of 439 provides the corresponding p-substituted acrylic acids or acrylates 440 (Scheme 7.145). In this context, ring-opening reactions of 4-bis [(methylthio)methylene]- and 4-bis[(benzylthio)-methylene]-, 4-(aIkylaminomethylene)-, 4-(dialkylaminomethylene)-, and other 4-heteromethylene-5(4//)-oxazolones have recently been described. 

Bis-4-arylidene-5(4//)-oxazolones are easily obtained from aromatic dialdehydes by the Erlenmeyer synthesis. Such bis(oxazolones) react with a,co-diamines to provide a convenient approach to macrolactams.Tandem Erlenmeyer condensation-macrolactamization (TECM) has been used to prepare analogues of naturally occurring, biologically active cyclic peptides such as bastadin-5. 

Aminolysis of 1,4-phenylene bis(oxazolones) 511 and subsequent cyclization to the bis-2-imidazolLn-5(4//)-ones 513 has also been described (Scheme 7.162). " A -(Sulfonamidophenyl)imidazolones are of particular interest as antineoplastic, antibacterial, and antifungal agents and a number of examples have been prepared analogously using the appropriate sulfonamidoaniline. ... 

Some examples of the Michael reaction on the exocyclic double bond of an unsaturated oxazolone have been discussed in previous sections. The synthesis of unsaturated 5(4//)-oxazolones from unsaturated 5(4/l/)-oxazolones via an addition-elimination sequence and the sequential reaction of unsaturated 5(4/i/)-oxazolones with a l,3-bis(nucleophile) have already been considered. This section will review Michael additions exclusively and, in this respect, a wide array of nucleophiles has been studied. 

Finally, new palladium(II) and platinum(II) complexes from 4-benzyl-4-methyl-2-phenyl-5(477)-oxazolone or C2 symmetric bis(oxazolone) ligands have been... 

Reaction of A-acylthreonines with Lawesson s reagent [2,4-bis(p-methoxyphen-yl)-l,3,2,4-dithiaphosphetane-2,4-disulfide] affords a mixture of unsaturated 5(4//)-oxazolones 801 and 5(4//)-thiazolones 802 (Scheme 7.245). ° °... 

Part B is comprised of the following five chapters Chapter 5—2(3H)-Oxazo-lones and 2(5H)-Oxazolones Chapter 6—4(5//)-Oxazolones Chapter 7—5(2//)-Oxazolones and 5(4//)-Oxazolones Chapter 8—2-Oxazolines and Chapter 9— Chiral Bis(oxazolines). 

There are four possible classes of bis-5(4 I)-oxazolones (cf. 8-11). Compounds of type 8 may be prepared by the Erlenmeyer reaction on dialdehydes. The compound in which R is derived from the 4,4 -dialdehyde of diphenyl ether (R =CeHj) is a recent example. ... 

Rao and Filler130 prepared a number of 2-phenyl-5,5-disubstituted 2-oxazolin-4-ones by base-catalyzed cyclization of halogenated bis-amides, such as a-chloro-a,a-diphenylacetylbenzamides [Eq. (30)]. When chloroacetamide reacts with oxalyl chloride, the bis-oxazolone (55) is obtained.138... 

The coupling partner, 2-phenyl-4-(trimethylstannyl)oxazole 1411 was readily prepared, in two steps, from 2-phenyl-4(5 /)-oxazolone. StiUe coupling of 1410 with 1411 using tetrakis-(triphenylphosphine)-paUadium[0] then afforded the model 2,4 -bis-oxazole 1412 in good yield. Similarly, 1410 was coupled with phenyltrimethyltin to generate 1413. 

The reaction of 4-phenyl-3-buten-4-olide with benzylamine was investigated as a model for polyamide synthesis. Linear polyamides were prepared from ringopening polyaddition of 4,4 -disubstituted bis(3-buten-4-olide) in m-cresol u g aliphatic diamines. Further studies have investigated the production of hydroxy-substituted polyamides from 4,4 -disubstituted bis(4-butanoiide) and polyamide production from 2,2 -p-phenylene bis-oxazolones by similar ring opening reactions with diamines. ... 

The 2,2-bis(tnfluoromethyl)-4-methyl-2f/-5-oxazolone, readily available from 2,2-bis(trifluoromethyl)-l,3-oxazolidin-5-one, is a synthetic equivalent of activated pyruvate [90] (equation 16). 

The reaction of ethyl A-arylcarbamates 3 with l-bromo-3,3-dimethyl-2-buta-none or l-bromo-3-ethyl-3-methyl-2-pentanone 4 in the presence of lithium bis(trimethylsilyl)amide (LiHMDS) results in the one-step synthesis of 3-aryl-5-ferf-butyl-2(3/T)-oxazolones 7 in fair to good yields (Fig. 5.2 Table 5.1, Fig. 5.3). This method is efficient for the preparation of bulky 5-substimted-2(37f)-oxazo-lones. 

Aromatic a-ketols 48 react with (diethylamino)tributyltin to afford a mixture of (Z)- and ( )-l,2-enediol-types of bis-organostannylated compounds 49 that cyclize upon heating with phenyl isocyanate to give a 3,4,5-triaryl-2(3/f)-oxazolone 50 (Fig. 5.14). ... 

Phosphites and 2,2-bis(trifluoromethyl)-5(2//)-oxazolone 71 react with elimination of carbon dioxide to give 2-aza-4-phospha-l,l-bis(trifluoromethyl)-l,3-butadiene 72 that can be used as a synthon for the previously unknown hydrogen-substituted nitrile ylide 72a in [3 + 2]-cycloaddition reactions. Examples of cycloadditions of 72a with dipolarophiles to give heterocyclic compounds 12t-ll are shown in Scheme 7.18. 

Alternatively, a spacer can be inserted between the heterocyclic rings to further modify the properties of the polymer. Although various spacers have been used, aromatic rings are probably the most frequently employed. In this case, 2,2 -(p-phenylene)bis[4,4 -dimethyl-5(4//)-oxazolone] 330 is the most common monomer (Fig. 7.34). Again, representative examples are described in selected references... 

Reaction of unsaturated 5(4//)-oxazolones with bis(nucleophiles) opens the way for the preparation of diverse heterocyclic compounds depending on the nucleophilic atoms of the reagent. First, if we consider nitrogen-containing bis(nucleo-philes), the reaction of anthranilic acid with unsaturated oxazolones 550 gives rise to substituted 3,l-benzoxazin-4-ones 551 (Scheme 7.174). " °... 

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