Synthesis dibenzo pyran-6-ones

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

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

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>. 

Hart, D. J., Kim, A., Krishnamurthy, R., Merriman, G. H., Waltos, A. M. Synthesis of 6H-dibenzo[b,d]pyran-6-ones via dienone-phenol rearrangements of spiro[2,5-cyclohexadiene-1,1 (3 H)-isobenzofuran]-3 -ones. Tetrahedron 1992,48, 8179-8188. 

As hereinbefore pointed out, the 5-(tertiary alkyl)resorcinols thus prepared in accordance with this invention are important intermediates in the preparation of useful drugs. For example, 5-(l,l-dimethyl-heptyl)resorcinol is utilized in the preparation of l-hydroxy-3-(l,l-dimethylheptyl)-6,6a,7,8,9,l 0,10a-hexahydro-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one, which compound is extremely useful in the treatment of depression in humans, as described in U.S. Pat. Nos. 3,928,598, 3,944,673, and 3,953,603. Similarly, 5-(l,l-dimethyl-heptyl)resorcinol is required in the synthesis of3-(l,l-dimethylheptyl)-6a,7,8,9,10,10a-hexahydro-6,6-dimethyl-6H-dibenzo[b,d]pyran-l,9-diol, which compound is useful as a blood-pressure lowering agent. It can thus be seen that a commercially feasible process for preparing 5-(tertiary alkyl)resorcinols in high yield is desirable. 

In 2012, Bodwell and Nandaluru applied a pyrrolidine-mediated six-step domino reaction process to the synthesis of 6 /-dibenzo[b,d]pyran-6-ones 59 (Schane 13.18) [29]. 

P. R. Nandaluru, G. J. Bodwell, Org. Lett. 2012,14,310-313. Multicomponent synthesis of 6//-dibenzo[fc,rl]pyran-6-ones and a total synthesis of cannabinol. 

O - Biaryl Carbamate DreM. Ring - to - Ring Carbamoyl Transfer and Alternate Synthesis of Dibenzo[b,d]pyran-6-ones... 

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