I was reading in Demosthenes, Against Conon (54.6). I translated a passage, and was not bothered a bit by it, and then one of my 4th year students said "what the heck is going on here?" I think the passage is just fine, and the major translations all agree with my sense; however, I can't find syntactical support for what both I and others do to the passage.
In the passage βούλομαι is used to control two separate clauses: the first clause is introduced by πρωτον μεν, the second by μετα ταυτα. Clearly these are parallel constructions. The μετα ταυτα clause adds the expected infinitive to βουλομαι, but the prior πρωτον μεν clause uses the nominative participle παρασχομενος, in concord with βουλομαι .
I can't find any discussion of such a participial construction with βουλομαι, or of a nominative participle being interchangeable with an infinitive. Of course, I am also half expecting Carl Conrad to immediately chime in with an obvious answer, quoting and citing from memory 3 examples from Xenophon, along with the page number of appropriate syntaxes

Daniel