Benzo 2/ naphtho pyran-6-ones

Particularly important is the influence of the metal countercation e.g., cleavage of the achiral lactone l,3-dimethyl-6//-benzo[ ,]naphtho[1.2-d]pyran-6-one in toluene at — 40 CC, using different metal alkoxides, e.g., (+)-menthol as inexpensive chiral 0-nucleophiles, gives atropisomer ratios of 81 19 for lithium, 66 34 for sodium, and 63 37 for potassium. In other solvents (e.g., THF), this selectivity order may be reversed14. 

The nucleus of the gilvocarcins, benzo[(/]naphtho[l,2-6]pyran-6-ones, has been derived in one step by the double annulation of a styryl sulfone with a phthalide <05JOC9017>. 

B. 1,3-Dimethyl-6H-benzo[b]naphtho[1,2-d]pyran-6-one (4). Under an argon atmosphere, a 250-mL, oven-dried, round-bottomed flask, equipped with a reflux condenser, is charged with freshly distilled N,N-dimethylacetamide (DMA, 130 mL), 3,5-dimethylphenyl 1-bromo-2-naphthoate (3, 3.24 g, 9.12 mmol), palladium(ll) acetate (205 mg, 0.913 mmol), triphenylphosphine (481 mg, 1.83 mmol), and sodium acetate (1.50 g, 18.3 mmol) (Notes 4 and 5). The orange suspension is degassed three times, placed in a preheated (130°C) oil bath (Note 5), and stirred at 130°C for 12 hr (Note 6). Removal of the solvent at 40°C (0.1 mbar, 0.075 mm) gives a black oily residue, which is Chromatographed (5 x 40 cm column, silica gel 0.063 - 0.2 mm, 170 g, 1 cm of charcoal at the top of the column eluent hexane / diethyl ether 5 1), to yield 2.00 g (80%) of the lactone 4 as a slightly yellow solid. Recrystallization from diethyl ether / hexane delivers 1.63 g (65%) of colorless or pale yellow crystals (Note 7). 

Dimethyl-6H-benzo[b]naphtho[ 1,2-d]pyran-6-one 6H-Benzo[b]naphtho[ 1,2-d]pyran 6-one, 1,3-dimethyl- (13) (138435-72-0)... 

Several dibenzo[6,tf ]pyran-6-ones (360) have been prepared by the reaction of substituted phenols with 2-methoxycarbonyl-l,4-benzoquinone in the presence of trifluoroacetic acid (79HCA2833). Treatment with silver oxide converts the products into the related quinones which may be elaborated to benzo[6]naphtho[[Pg.800]

Outten, R A, Daves, D G Jr, Benzo[d]naphtho[l,2-h]pyran-6-one C-glycosides. Aryltri-n-hutylstannanes in palladium-mediated coupling with 2,3-dihydropyran and furanoid glycols, J. Org. Chem., 54, 29-35, 1989. 

Farr, R N, Kwok, D I, Daves, G D Jr, 8-Ethenyl-l-hydroxy - 3-D-ribofuranosylbenzo[d]naphtho[l, 2-b ]pyran-6-one and 8-ethenyl-1 -hydroxy-4-(2 -deoxy-p-D-ribofuranosyl)benzo[d ] naphtho[ 1,2-b ]pyran-6-one. Synthetic C-glycosides related to the gilvocarcin, ravidomycin, and chrysomycin antibiotics, J. Org. Chem., 57, 2093-2100, 1992. 

The condensation of salicylaldehyde or its derivatives with various derivatives of ethyl acetate in the presence of piperidine led to the synthesis of coumarins 95 in 55-94% yields under solvent-free conditions using MWI. Similarly, the benzo analogs 96 were prepared in 75-82% yields from 2-hydroxy-1-naphthaldehyde within 3-lOmin (Scheme 19) (98JCR(S)468). However, naphtho[2,l-Z ]pyran-3-ones 96 were prepared in 58-67% yields from the same aldehyde and substituted acetic acids under MWI for 6-8 min but in the presence of DCC and using DMSO as a solvent (Scheme 19) (97JCR(S)178). 

Tetrahydro-2-[4-(2-thienyl)-l-buten-3-ynyl]-2i/-pyran-3-ol, see R-30007 lb, 126,13,14c-Tetrahydro-1,3,4-trihydroxy-14//-benzo[c]naphtho[2,1,8-AW a]xanthen-14-one, see 0-20030... 

Phenols (e.g., phenol itself [CeHs-OH or Ar-OH], Table 6.10, item 2) and their esters (e.g., the trifluoroacetate ester of phenol [C6H5-O2CCF3 or Ar02CCH3], Table 6.10, item 3) have been oxidized with air and oxygen (O2), in neutral and alkaUne solutions, with and without ionic and/or radical catalysts and/or irradiation and in a variety of solvents. Enzymes (this chapter and Chapter 12) from a wide variety of sources have also been used. Frequently, oxidation of aromatic systems to phenols cannot be stopped before quinones and products of ring fragmentation occur and numerous, sometimes ill-defined, products result. Thus, as shown in Equation 6.80, oxidation of the polynuclear hydrocarbon chrysene with anunonium cerium(IV) sulfate [ceric ammonium sulfate, Ce(NH,)4(S04)4] is reported to produce 6H-benzo[d]naphtho[l,2-/>]pyran-6-one (8% yield) and a quinone (23% yield). The remainder of the product(s) (69%) was unidentified. 

Thiolate-bridged dirutheniutn complexes catalyze the [3-f3] cycloaddition reaction between propargylic alcohols and cyclic 1,3-dicarbonyl compounds to afford 4,6,7,8-tetrahydrochromen-5-ones or 4//-cyclopenta[b]pyran-5-ones [193] and with 2-naphthols or phenols to afford l//-naphtho[2,l-b]pyrans and 4//-l-benzo-pyrans, respectively [194]. This cycloaddition is considered to proceed by stepwise propargylation and intramolecular cyclization (carbon and oxygen nucleophile additions) reactions, where ruthenium allenylidene and vinylidene complexes are the key intermediates (Scheme 57). Enantioselective mthenium-catalyzed [3-f3] cycloaddition of propargylic alcohols with 2-naphthols has also been described [195]. 

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