It can be prepared in several different ways: 1) The reaction of phthalide (I) with disodium 3-hydroxyphenylacetate (II) at 225 C gives 3-(2-carboxybenzyloxy)phenylacetic acid (III), which is then cyclized with PPE (polyphosphoric ester) at 120 C (1,2). 2) The reaction of (III) with refluxing SOCl2 yields the corresponding diacyl chloride (IV), which is then cyclized with AlCl3 in toluene (3).
3) By oxidation of 6,11-dihydro-11-hydroxydibenzo[b]oxepin-3-acetic acid (V) with MnO2 in benzene (4). 4) By hydrolytic decarboxylation of ethyl (6,11-dihydro-11-oxodibenzo[b,e]oxepin-3-yl)cyanoacetate (XII) with NaOH in refluxing ethanol (7). 5) By hydrolysis of 6,11-dihydro-11-oxodibenzo[b,e]oxepin-3-acetonitrile (XIII) with NaOH as before (2). 6) By oxidation of 6,11-dihydrodibenzo[b,e]oxepin-3-acetic acid (XVII) with MnO2 in hot benzene (2).
7) The reaction of 6,11-dihydro-11-oxodibenzo[b,e]oxepin-3-acetyl chloride (VI) with CH2N2 gives the corresponding diazoacetyl derivative (VII), which by a Wolff rearrangement with Ag2O and ethanol affords the ethyl ester (VIII). Finally (VIII) is hydrolyzed with NaOH as usual (5). 8) The rearrangement of 3-acetyl-6,11-dihydro-11-oxodibenzo[b,e]oxepine (lX) with TlNO3 in ethanol with perchloric acid yields the ester (VIII) (2). 9) By rearrangement of (IX) with a solution of sulfur and H2S in concentrated ammonia at 160-70 C in a sealed tube (2).
10) The oxidation of 3-vynyl-6,11-dihydro-11-oxodibenzo[b,e]oxepine (X) with TlNO3 in methanol gives the acetaldehyde derivative (XI), which is finally oxidized with KMnO4.
11) The reaction of (6,11-dihydro-11-oxodibenzo[b,e]oxepin-3-yl)-formaldehyde (XIV) with formaldehyde dimethylmercaptal S-oxide (XV) in refluxing THF gives 1-(methylsulfinyl)-1-(methylthio)-2-[3-(6,11-dihydro-11-oxodibenzo[b,e]oxepinyl)]ethylene (XVI), which is then hydrolyzed with HCl in refluxing THF.