The Sinister Six first appeared in Spider-man Annual #1. The “team” formed after Doctor Octopus got out of jail, and frustrated by his losses to Spider-man, called upon every villain he knew to get help in defeating him. The only ones to respond were Kraven the Hunter, Mysterio, Electro, Vulture and Sandman.
The problem with them coming together was that none of wanted to work directly together to defeat Spider-man except Vulture, so they all individually took him on. Naturally they were all defeated in that same issue, because in those days they could tell a story and wrap it up in the same issue.
Hasbro revealed during Toyfair 2017 a box set featuring all six characters and Spider-man in the 3.75″ scale. This set is currently up for preorder exclusively on Amazon.
The box features artwork of the original annual on the spine and has Spider-man featured on the front in a little bubble. The back shows all the figures in the set.
This is a neat set that I would be interested in if it was in the six-inch scale. If it was in the six-inch scale, that would mean we would be getting a Doctor Octopus, Comic Vulture and Mysterio in this scale. Hopefully we get them soon. Usually when they make a figure in the smaller scale first, the larger scale comes later.