The distances are too great.
The way to get this done in 1942 would be a different Barbarossa where the Soviet Union collapses completely. You probably get the Black Sea fleet surrendered or scuttled anyway in this scenario, without the German army having to physically occupy the entire coast line. But, yes, then you can have German units reach the Turkish border in 1942 as part of the mopping up operations. The point is that as long as the Red Army is a cohesive force in 1942, it can block any advance in that area.
Though its much less likely, you can do this in 1943. Either the Germans win a huge battle for Moscow in 1942 and the Soviet Union collapses and you are back to the earlier scenario. Or they pull off a modified, better organized, Case Blue where in 1942 the Volga is secured (and Sevastopol taken) with no attempt to advance to the Caucasus, cutting the Caucasus and Black Sea off from the rest of the Soviet Union. Then in 1943 the Caucasus/ Black Sea is taken in another offensive. We will jump up and down and wave our hands to deal with the Allied attempts to stop this, including from British and American army and air units based out of Iran.