Iran going wild on wheat!
There is apparently more than sanctions going on. It may be they are having a very dry situation and fear for domestic production, which could no doubt cause fear among leadership that economic hardship is one thing but, hunger can doom governments. It's normal for Iran to import wheat but the purchase of up top 3 million tons in a month or two is unusual. They are also trying to arrange imports of millions more tons from Pakistan and India - both problematic sources for quality. And they just bought 120,000 tns from the US.
American policy is food is not to be used as a weapon (a lesson learned when sanctions on Pakistan caused a crisis after they retaliated to India's massive nuclear tests with similar actions in the 90's). The sanctions on Iran are restrictions on financial institutions dealing with Iran, not food, though it affects their ability to finance purchases.