Benzomorphans rearrangement products

The structure of the rearranged product 114 is very similar to that of the benzomorphan, like pentazocine (Fig. 23) [105, 106], a useful analgesic. Although several papers have previously described the total synthesis of pentazocine, many... 

Similarly, Bosch and co-workers(39) isolated from the potassium hydroxide-induced rearrangement of l,3,4-trimethyl-l-(3,4,5-trimethoxy-benzyl)-l,2,5,6-tetrahydropyridinium chloride, products corresponding to 73, 99, and by inference 101, together with a Hofmann-elimination product. An unambiguous method for preparing 2-benzyltetrahydropyridines from 2-bromopyridine, thus affording a wide selection of substituted benzomorphans has been published.(39a)... 

The synthesis of benzomorphans substituted in the 11-position from a 2-tetralone (Scheme 4.2, p. 157) involves either thionyl chloride dehydration of an 11-methylcarbinol (13a)(9) or a pyrolysis of the corresponding acetate perchlorate (136)methylene derivative (14). Carbocation-mediated processes in bridged compounds of this type are likely to give rearrangement byproducts. Kugita and Takeda(124) isolated from the thionyl chloride route an unstable chloride (203), and the indenotetrahydropyridine (204). Other reports(30 96a,125) of unidentified products from these reactions resulted in an investigation 126 127 of both pathways (Scheme 4.20). 

---