Benzo[b]furan dimers

1. A compound of the formula I

wherein

L is selected from —(CH 2 ) a —, and a group of the formula

—B—A—B—

wherein a is selected from 2-20,

B is —(CH 2 ) b —, —(CH 2 ) c —O—(CH 2 ) d —, or

and

A is selected from a group of the formula

wherein R 4 is selected from halogen, lower alkyl, lower alkoxy, NO 2 , and —NRR,

D and E are independently selected from O, S, Se, CRR and NR,

b is selected from 1-10,

c is selected from 1-8,

d is selected from 1-8,

e is selected from 0-4;

f is selected from 0-3, and

R is selected from H, lower alkyl, aralkyl and aryl;

X is selected from O, or —NH—;

R 1 is selected from

a C 1 -C 20 alkyl which may be unsubstituted or substituted with one or more substituents selected from CN, halogen, lower alkoxy, thio-lower alkyl, nitro, phosphinos, phosphates, and protected amino;

a C 1 -C 20 alkenyl which may be unsubstituted or substituted with one or more substituents selected from CN, halogen, lower alkoxy, thio-lower alkyl, nitro, phosphinos, phosphates, and protected amino;

an aromatic group which may be unsubstituted or substituted with one or more substituents

selected from halogen, lower alkyl, lower alkoxy, thio-lower alkyl, nitro, phosphinos, phosphates, and protected amino; and

an aralkyl which may be unsubstituted or substituted with one or more substituents selected

from halogen, lower alkyl, lower alkoxy, thio-lower alkyl, nitro, phosphinos, phosphates, and protected amino;

R 2 is selected from halogen, hydroxy, CN, nitro, lower alkyl, lower alkoxy, thio-lower alkyl, lower alkenyl, cycloalkyl, C 2 -C 8 acyl, lower alkyl ester, and lower alkyl amide;

R 3 is a group of the formula

—(CH 2 ) p —Y q —(CH 2 ) r —Z s —(CH 2 ) t —R 5

 wherein Y and Z are independently selected from O, S, —OCH 2 CH 2 O—,

p, r and t are independently selected from values from 0 to 10;

q and s are independently selected from 0 and 1, provided that when t=0 then s=0, and when r=0 then q=0; and

R 5 is selected from OH, CO 2 H,

n is selected from 0-4; and

m is 0 or 1, with the proviso that the sum of n plus m does not exceed 4.

2. A compound of the claim 1 , wherein A is selected from a group of the formula —O—, —CH═CH—, and —C≡C—C≡C—.

3. A process for the preparation of a compound of the formula I

comprising the steps of

(a) a Sonogashira reaction to prepare a compound of the formula III

by reacting a compound of the formula IV

with a terminal alkyne represented by the formula V:

in the presence of base and a transition metal catalyst;

(b) carbonylative annulation to give a compound of the formula II

by treating a compound of the formula III with an alcohol of the formula R 0 —OH in the presence of a transition metal catalyst, carbon monoxide and a base, wherein

R 0 is lower alkyl, aralkyl, or aryl, wherein the lower alkyl, aralkyl, or aryl, may be optionally substituted with one or more halogen, CN and nitro, or R 0 is selected from a group of the formula

—L—OH, and —B—A′,

wherein L and B are as described above for a compound of the formula I, and A′ is —CH═CH 2 or —C≡CH ; and

(c) coupling two molecules of the formula II to give a compound of the formula I,

wherein R 1 , R 2 , R 3 , X, L, n and m are as described in claim 1 for the compound of the formula I.