Reactions of the HCN-tetramer with aldehydes.

The HCN-tetramer, a 'classic' of the prebiotic chemistry of HCN, is shown to undergo a remarkable reaction with acetaldehyde in slightly basic or neutral aqueous solution at room temperature. The reaction consists in an aldolization-type C,C-bond formation, accompanied by a (presumably aldehyde-catalyzed) hydration of one of the two nitrile groups and the formation of two cyclic aminal-type groupings, each of the latter incorporating an additional molecule of the aldehyde. Should this so far unexplored type of chemistry of the HCN-tetramer prove to have some generality, the finding might add a new dimension to the potential etiological relevance of this HCN-oligomer.