6-Dibenzo pyrans

In the application of oxidation dyes, aromatic amines form insoluble polyazine derivatives in the fiber (azine dyes [81]). Synthesis proceeds in several steps in a hydrochloric acid medium by oxidation (e.g., with dichromate). For the chief representative of this group, aniline black, the chromophore consists of dibenzo-pyran rings. Oxidation dyes are rapidly decreasing in importance because aniline and other aromatic amines as well as the bichromate used for oxidation are toxic. The colors produced by aniline black are characterized by a full bluish black shade and excellent fastness. Since they are easily reserved, they are still used occasionally for printing grounds. For individual processes, see [82],... 

An unusual C — H activation on orf/zo-methoxy groups was observed by Dyker et al., in the reaction of methoxyiodoarenes such as 144 leading elegantly to 6//-dibenzo[/ , /]pyrans such as 145 (Scheme 3-38) [190,191]. Under the same conditions, 2-rert-butyliodobenzene (146) with various aryl halides gave the benzocyclobutene derivatives 147, the formation of which also involves an alkyl C — H activation [190e]. 

TETRAHYDROCANNABINOLS Merck Index i 9142 12 9349] tetrahydro- 6,6)9-mmethyl-3--penty]-6iir-dibenzo [, ] pyran-i-ol THC Marinoi, dronabinol... 

Dibenzo[W]pyrans are formed when o-(bromomethyl)phenyllead triacetates are heated with phenols (Scheme 14) <01TLS875>. Fused dibenzo -pyrans and -thiopyrans result from the cycloaromatisation of the non-conjugated tetraynes 15 (Scheme 15) <01H(54)887>. 

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... 

CN (6a/f-rianj)-6a,7,8,10a-tetrahydro-6,6,9-trimethyl-3-pentyl-6//-dibenzo[fc,if pyran-l-ol... 

The 3,4-didehydro-27f-l-benzopyran (4), generated when 3,4-dibromochromenes are treated with organometaUic reagents, reacts with dienes to give the dibenzo[6,d]pyran system <96TL1313>. 

Naturally occurring oxaarenes based on polycyclic pyrans encompass a plethora of structures including the plant polyphenols such as anthocyanins and a-tocopherol (vitamin E). Halogenated dibenzo-p-dioxins and dibenzofurans are formed both as by-products during the manufacture of chlorophenols, and from the incineration of organic matter in the presence of inorganic halides. 

The chemical name of A9-THC according to the dibenzopyrane numbering system is 3-pentyl-6,6,9-trimethyl-6fl,7,8,10fl-tetrahydro-6H-dibenzo-[b, d]pyran-l-ol as depicted in 1.1 (Fig. 1). 

Ethyl 2-methoxy-617-dibenzo[b,[Pg.12]

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... 

Dronabinol. Mafinol ( R-/ra. f)-6, 7,8,10 -tetrahydro-6,6,9-trimethyl-3-pentyl-6IT-dibenzo(B,D) pyran-l-ol is the principal psychoactive substance present in Cannabis sativa E, ie, marijuana. It is a controlled substance, formulated in sesame oil and encapsulated in soft gelatin capsules for oral administration. 

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]

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