A tome I read about Stalingrad said that Stalin, in a weak moment within the first 60 days of the invasion, was willing to concede these in a peace treaty if Hitler would stop the offensive. It was the Bulgarian Ambassador who assured Stalin, that, ultimately, Russia would prevail, if they just had the willpower, in a war of attrition.
You can find a detailed discussion of Hitler’s overall eastern strategy, before the war began, in Paul Carell’s “Hitler Moves East.” A superb read..