In Greek masculines of the first declension borrow the singular genitive ending -ου from second declension. Latin uses the ending -ae for all of first declension: puellae, nautae, Anchisae, Aeneae. There are also occasional genitives similar to the Greek first declension ones (familias, musices, Melpomenes), but these are besides my point.
Was -i ever used as a genitive ending for masculines of the first declension? If this happens, it is presumably due to Greek influence, and I suspect it is more likely to happen in words or names of Greek origin. Despite seeing many Greek loan words, I have never seen this genitive in any text or grammar. Searches for nauti and Anchisi give nothing, and Aenei gives unrelated hits for the adjective aēneus.