Cyclopenta benzofurans

A variety of 3-substituted coumarins react with an excess of dimethylsulfoxonium methylide, presumably forming the 3,4-fused cyclopropane derivative which rearranges to the cyclopenta[ >] benzofuran (95TL5603). 

Research and development of Beraprost sodium, a stable modified prostaglandin PGI2 possessing cyclopenta[d]benzofuran fragment 96YGK1055,97YZ509. 

A solution of 482 mg of 7-chloromethyl-3-methyl-trans-4a-cisoid-4a,5a-cis-5a-l,4a,5,5a,10b,10c-hexahydrodioxino[5,4-a]cyclopenta[b]benzofuran in 5... 

When coumarins shown below having an electron-withdrawing group at the C-3 position were treated with 2.4 equiv. of dimethylsulfoxonium methylide at room temperature in DMF or DMSO, novel tricyclic 2-substituted-cyclopenta[6]benzofuran-3-ols were obtained in moderate to good yields. A mechanism was proposed, and the key intermediate related to the proposed approach was provided <02T1497>. 

Addition of secondary and tertiary enaminones derived from 1,2-cyclohexanediones as dienophiles to acetylbenzoquinone leads in a hetero-Diels-Alder reaction to benzo[c]-chromentriones. The Diels-Alder adducts are unstable and rearrange easily to condensed benzofurans. They can be converted by acids to a carbazolone derivative in low yield and to cyclopenta- and cyclohexa[c]isoquinolinium salts in fair yield32 (equation 246). 

For the preparation of the benzo[i>]cyclopropa[d]pyran 2-599, Ohta and coworkers have treated 3-ethoxycarbonylcoumarin (2-597) with dimethylsulfoxonium methylide (2-598), derived from the corresponding trimethylsulfoxonium iodide and NaH (Scheme 2.136) [307]. The isolated product was not 2-599, however, but an unexpected cyclopenta[i>]benzofuran derivative 2-600 probably formed through 2-599. 

In the total synthesis of ( )-linderol A, the 6, 5-tricyclic cyclopenta[i>]benzofuran was made by a tandem reaction of a 3-ethoxycarbonylcoumarin derivative with dimethyl sulfoxonium methylide <03JOC1216>. 

Enantioselective Intramolecular Cyclization (Sn2 reaction). The desymmetric transformation of meso-structures has been recognized as a versatile synthetic method for optically active compounds in organic enzymatic processes. The enantioselective intramolecular cyclization of the bis-phenyllithium species, which is generated by addition of butyllithium to a solution of cis-3,5-di(bromophenoxy)cyclopentene, has been attained by addition of lithium salt (1.2 equiv) of (/ )-BINOL-Me to produce a cyclopenta[fc]benzofuran with 87% ee (eq 18). ... 

The synthetic strategy involving an intramolecular hydroxyl epoxide opening was applied to build up the cyclopenta[i)]benzofuran ring for the total synthesis of the naturally occurring rocaglaol <04OL4595>. 

The tricyclic cyclopenta[Z ]benzofuran skeleton of rocaglamide47 (an antileukemia agent extracted from Aglaia elliptifolid) has been successfully produced by sunlamp irradiation of 46 in the presence of diphenyldisulfide (equation 41). This work is connected to the... 

---