Hold it... I'm not saying the other steps are valid
.
I'd like to offer some advise on the methylenation of catechol though. Using diiodomethane is not necessary. Rhodium's site has a page about methylenation reactions for catechol that work just great with dichloro- and dibromomethane. Considering the fact that DCM gives reasonable to high yields in the methylenation of catechol, there is no good reason to use dibromo- or diiodomethane other than spoiling money and organic reagents. The use of a good solvent (DMF or DMSO) is of high importance...
However, if you still want to peform the methylenation reaction with DIM and catechol, here are some references to synthesize it from other substances:
triiodomethane ---> diiodomethaneHofmann. Ann 115 (1860) 267
Butlerow. Ann Chim <3> 53 (1858) 316
Auger. CR 146 (1908) 1281
Organic Synthesis Collection Vol I p 358 (you know the website)
Nad'. Izv Akad Nauk SSSR Ser Khim (1957) 1144 (Eng translation)
Gutmann. Chem Ber 52 (1919) 213
DE Jackson. Phytochemistry 23(5) (1984) 1029
Nef. Ann 308 (1899) 325
dichloromethane ---> diiodomethanePerkin. JCS 119 (1921) 1402 (NaI in acetone)
Laskina. Zh Prikl Khim 32 (1959) 895 (Eng translation) (NaI in benzyl alcohol)
Hoeland. Ann 240 (1887) 241 (dichloromethane and iodine)
chloroform ---> diiodomethaneLieben. Z Chem (1868) 713