2-Furanone ring with

Furan as solvent in Grignard reactions 16, 679 2-Furanone ring with rearrangement 16, 764 2-Furanones... 

Sodium methoxide 2>Furanone ring with rearrangement... 

A frequently used transformation of a five-membered ring with one heteroatom to a pyrazol-3-one is that from furanone derivatives. 

The more utilitarian means for installing an aryl substituent in position 4 onto the 2(5//)-furanone ring, the Suzuki-type cross-coupling of arylboronic acid with... 

The addition followed a radical chain mechanism initiated by photoinitiated electron transfer from the tertiary amine to the excited aromatic ketone and occurred with complete facial selectivity on the furanone ring (99TL3169). The yields increased and best results were obtained with sensitizers (4-methoxyacetophenone,... 

Treatment of 3-(2-furylmethylene)-5-aryl-2(3//)-furanones (38) with A1C13 in benzene led to alkyl-oxygen ring cleavage to give resonance stabilized carbocations 39, which upon electrophilic attack in the ortho position yield the corresponding benzofurancarboxylic acids (40) (Scheme 12) (77JPR689). 

The reaction of 3-bromo-2-hydroxychromanone (657) with sodium methoxide also results in pyran ring cleavage followed by the formation of a furanone ring (75JHC981). 

A six-step synthesis of hexahydrofuro[3,2-3]oxepin-2(3/7)-one involves cyclization with the formation of an ethereal C-0 bond (Scheme 13). However, its specific peculiarities are that the product skeleton is built from tetrahydrofuran (THF) and furan, the key reactions being the oxidation of a furan ring with singlet oxygen, followed by an intramolecular Michael addition to 2(5/7)-furanone C=C bond <2003TL4467, 2004TL5207>. 

H. Lerche, M. Pischetsrieder, and T. Severin, Maillard reaction of D-glucose identification of a colored product with conjugated pyrrole and furanone rings, J. Agric. Food Chem., 2002, 50, 2984-2986. 

Aurones (Phe C40(=0)=CH-Phe). Aurones (2-benzylidenebenzofuranones) derive from oxidation and cyclization of chalcone precursors to yield the corresponding benzofura-none (benzene fused with a five-membered furanone ring) Phenyl-CO- CH=CH—Phenyl + O2 — Benzofuranone = CH-Phenyl. Various aurones inhibit iodothyronine deiodinase, namely (numbering 1-9 in the bicyclic benzofuranone and 1 -6 in the benzylidene phenyl) aureusidin (4,6,3, 4 -tetrahydroxyaurone), bracteatin (4,6,3, 4, 5 - pentahydroxyaurone), maritimetin (6,7,3, 4 -tetrahydroxyaurone) and sulfuretin (6,3, 4 -trihydroxyaurone). 

The addition occurs with complete facial selectivity on the furanone ring. The method has been generalized to the addition of tertiary amines and A-protected secondary amines to electron-deficient olefins (Table 13). 

By treatment with NaH, bicyclic furoisoxazolidines 192 failed to give the expected 3-alkyl-substituted 2-amino-butenolides 193, but instead afforded the 3-amino-2(577)-furanones 195 with conservation of the lactone ring and fragmentation of the isoxazolidine nucleus. In this case, the initially formed anion evolved to 194 with formation of an endocyclic double bond and elimination of formaldehyde (Scbeme 45). The two-step process - intramolecular 1,3-dipolar cycloaddition and NaH treatment of the furo[3,4-( ]isoxazolidine adducts - was applied to the synthesis of enantiopure 3-alkylamino-5-methyl-2(5/7)furanones <2002JOC4380>. 

A better cyclodehydrating process was performed by phosphorus pentachloride in dimethoxyethane at room temperature. The synthetic potentiality of the furanone ring of 104 in the synthesis of functionalized 1,2,3-triazoles by the cleavage with ammonia and amines has been explored. 

These compounds are divided into two main types. The first has the quinoxaline ring fused to the 2 and 3 positions of the furanone ring, whereas the other type has that ring fused to the 3 and 4 positions. These compounds were prepared from quinoxalinones or quinoxalines obtained from the reaction of furantriones with one or two molar equivalents of o-diamines... 

Irradiation of the furanone derivative (77a) affords the two products (78) and (79) shown in Scheme 5. When the oxygen function at C-2 is not methylated (77b), irradiation yields the products (80, 81) (Scheme 6). In this case a different rearrangement mechanism is permitted as a result of the relative ease of opening of the furanone ring. The route to product (80) is thought to involve a Norrish Type II process of the carbonyl group with the proximate methoxy function. Subsequent rearrangement via the spiro intermediate (82) ultimately provides the product (80). In the first example (Scheme 5) the formation of (78) also involves... 

Similarly photocycloaddition of ethylene with chiral 5-alkoxyfuranones 181 proceeds with facial diastereoselection [153], Although selectivity remains low, the reaction has been used for the enantiospecihc synthesis of grandisol because it is easy to separate the initial diastereoisomers [154]. Selectivity is greatly influenced by temperature and by substituents on the ethylenic bond of the furanone ring. It was concluded that steric hindrance of the alkoxy group and stereoelectronic effects of substituents on the conjugated system are responsible for the selectivity observed. It was also proposed that the diastereoselection of the photocycloaddition of ethylene with 181 was dominated by the approach of ethylene to the vibrationally relaxed (71,71 ) excited furanone rather than by the selectivity of the reactions of biradicals. 

CigHigOj, Mr 326.35, crystals, mp. 157-158 °C (E-form). Antitumor principle from the leaves of Geijera parviflora (Rutaceae). A dihydro form with a hydrogenated furanone ring, C19H20OS, Mr 328.36, also isolated from G. parviflora and possessing cytostatic activity is known as well. ... 

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