Without quoting any experts, common sense dictates that domestic cats cannot, or should not on ethical grounds, mate with a lion or tiger or any other big cat species for several reasons. Firstly, their size difference is too large to make it practical. Secondly, in an encounter between a big cat and the much smaller domestic cat the big cat would regard the smaller cat as prey. The practical issues would be insurmountable it seems.
Male lion and female domestic cat
The best source for this kind of information is Sarah Hartwell and she states on her website messybeast.com that even artificial insemination would be unlikely to result in a successful pregnancy because of the differences in size and gestation periods between the two species.
Also, the domestic cat’s womb would not be able to accommodate the large fetus of a lion. The fetus would be miscarried when it reached full-term kitten size.
Female lion and male domestic cat
If a female lion carried a hybrid offspring to full-term, Sarah says that the cubs would be smaller than purebred cubs. She says that undersized offspring ready survived. This implies, by the way, that putting aside the practical issues if a male domestic cat mated with the female lion they might produce offspring but that they wouldn’t survive. Sarah does not say that genetically it is impossible.
However, the species are different genetically and they belong to a different taxonomic genera. Even when tigers mate with lions to create ligers and tigon there are major problems. The Wild Cat Sanctuary states that ligers often have to be born by cesarean section because they are “predisposed to gigantism”. Many fail to survive and tigons rarely survive infancy. They also suffer from neurological and physical issues and can experience dwarfism.
Were not told about these huge problems when lions and tigers are forced to mate by zoos keepers such as the infamous Joe Exotic. There’s also the issue of sterility in exotic cat breeds. For example, male F1 Savannah cats are sterile (serval x domestic cat).
The domestic cat does sometimes mate with the smaller wild cat species such as the Scottish wildcat which, ironically, has arguably resulted in the extinction of the Scottish wildcat in the wild i.e. there are no purebred Scottish wildcat left. A substantial proportion of African wildcats in Africa are hybrids, crosses between domestic cats and wildcats.
I’m not sure that somebody has tried to mate a domestic cat with a lion. We don’t know, therefore, exactly what would happen. However, all the research that I have done indicates that it is both impractical and genetically impossible to result in a successful outcome. There is also the moral dimension. I think you would find it hard to justify such an experiment because it would be pointless and essentially cruel.