6//-Dibenzo pyran-6-ones

H-Dibenzo[6,/]plumbepin, 10,11-dihydro, 1, 627 Dibenzo[6,d]pyran-6-ones synthesis, 3, 800... 

Chemical Name 1-Hvdroxy-3-(1, 1 -dimethylheptyl)-6,6-dimethyl-6,6a,7.8,10,10a-hexahy-dro-9H-dibenzo(b/Jl pyran-9-one... 

A solution of 1.5 g of dl-3-(1, r-dimethylheptyi)-6,6a,7,8-tetrahydro-1-hydroxy-6,6-di-methyl-9H-dibenzo(b,d] pyran-9-one in 50 mi of anhydrous tetrahydrofuran (THF) was added dropwise to a soiution of iithium metal in liquid ammonia at -80°C. Excess iithium metal was added in chunks to the solution as the biue color, indicating free dissolved lithium, disappeared. After the addition was complete, ammonium chloride was added to react with any excess lithium metal still present. 

The mixture was then allowed to warm to room temperature in a nitrogen atmosphere during which process the ammonia evaporated. The reaction mixture was then acidified with 1 N aqueous hydrochloric acid, and the organic constituents extracted with ethyl acetate. The ethyl acetateextracts were combined, washed with water and dried. Evaporation of the ethyl acetate under reduced pressure yielded 1.4 g of crude dl-trans-3-(r,r-dimethylheptyl)-6,6a, 7,8,10,10a -hexahydro-1 -hydroxy-6,6-dimethyl-9H-dibenzo(b/J] pyran-9-one. The... 

Five-membered oxygen- and sulfur-containing heterocyclic ketones reveal notable reactivity (03RCB961, 03RCB1380). Benzo[fc]furan-3-one 204 with arylidenemalononitriles 30 gives dibenzo[b,d]pyrans 206 instead of expected pyran 205 as a result of Michael reaction and the exchange of methylene components (03RCB961) (Scheme 77). 

Similarly, the structure of a nitro-PAH lactone found in ambient aerosols and also formed in laboratory irradiations of phenathrene-NO -air mixtures, 2-nitro-6//-dibenzo[h,rf]pyran-6-one, which is a powerful, direct-acting bacterial mutagen and potent human cell mutagen, is commonly shown as (XI) (Helmig et al., 1992a Arey et al., 1992 Sasaki et al., 1995, 1997b Arey, personal communication). 

In the early 1990s, several nitro-polycyclic aromatic compounds that are powerful direct mutagens were identified in ambient particulate matter, including the nitrophenanthrene lactones 2- and 4-nitro-6//-dibenzo[6,r/]pyran-6-one, whose mutagenicities are given in Table 10.20. The 2-isomer (XI) is not only very... 

Lewis acids have also been found to promote the electrophilic cleavage of cyclobutanes. The key feature of this reaction can be depicted by the conversion of the chiral 4-(2-hydroxy-6-methoxyphenyl)-6,6-dimethylbicyclo[3.1.1]heptan-2-ones 5 and 4-(2-methoxy-6-hydroxyphenyl)-6,6-dimethylbicyclo[3.1.1]hept-3-en-2-ones 7 to (6a5, 10a/ )-(-)-l-methoxy-6,6a,7,8,10,10a-hexahydro-6,6-dimethyl-9//-dibenzo[b,c/]pyran-9-ones 6 and (6aS)-( + )-methoxy-6,6a,7,8-tetrahydro-6,6-dimethyl-9//-dibcnzo[b//]pyran-9-ones 8, respectively, on treatment with either tin(IV) chloride in chloroform or with aluminum trichloride in dichloromethane.52... 

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]

Zhang H-W, Huang W-Y, Song Y-C, Chen J-R, Tan R-X (2005) Four 6//-Dibenzo[b,rf] pyran-6-one Derivatives Produced by the Endophyte Cephalosporium acremonium IFB-E007. Helv Chim Acta 88 2861... 

A solution of 1.5 g of dl-3-(r,r-dimethylheptyl)-6,6a,7,8-tetrahydro-l-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one in 50 ml of anhydrous... 

Benzene-EtOAc Visual Another name for nabilone ( )-trans-3-(1,1-dimethylheptyl)-6,6a,7,8,10,10a-hexahydro-1 -hydroxy-6,6-dimethyl-9H-dibenzo [b,d] pyran-9-one (446]... 

A substituted dibenzo[7,4]thiopyran results when the carbanion derived from thiochroman-4-one reacts with the highly substituted 277-pyran-2-one 411. Initial attack at C-6 prompts cyclization at the 4-position of the thiochroma-none unit and subsequent decarboxylation and dehydration account for the formation of the product (Equation 116) <2004EJ0886>. 

The reaction of carbanions derived from tetrahydrothiopyran-4-one and its benzologue with the pyran-2-one 500 (X = COzMe, Y = MeS) affords isothiochromans and 67/-dibenzo[AY]thiopyrans, respectively, through a carbanion-mediated annulation sequence outlined in Scheme 185. In the latter case, the actual product depends on the amount of base used with an excess, Michael addition of hydroxide ion is preferred to a cyclocondensation and results in the displacement of MeS and formation of a hydroxy-substituted dibenzo[AY]thiopyran <2001JOC5333, 2002J(P1)1426>. 

Scheme 38. Biaryl O-carbamate DreM. Ring-to-ring carbamoyl transfer. Synthesis of dibenzo[b,d]pyran-6-ones.

Furthermore, Z-3-bromo-propcnoates 148 are suitable substrates for Sonogashira-[4 + 2]-cycloadditions to furnish 6H-dibenzo[M]pyran-6-ones 149 in moderate to excellent yields as shown by Yamamoto and... 

A series of dibenzofuran-l,4-diones illustrated in the following scheme were constructed via a DDQ-mediated intramolecular oxidative cyclization of quinone-arenols <070L2807>. Dibenzo[b] furans were also found to be made from 2//-pyran-2-ones and 6,7-dihydro-577-benzo[Z>]furan-4-one <07T1610>. The asymmetric synthesis of chiral furo-fused BINOL derivatives was achieved via copper(II)-mediated oxidative coupling from naphthofuranol in the presence of chiral phenylethylamine <07TL317>. 

---