1,1′,3,3′‐Tetraalkyl‐2,2′‐biperimidinylidenes: Unexpected substituent effects on the reactivity of carbon–carbon double bond

C₂ deprotonation of 1,3‐dibutylperimidinium bromide ( 1a ) with sodium hydride and a catalytic amount of potassium tert‐butoxide in dry THF led to the formation of the exceptionally inert tetraaminoalkene 2a . In contrast, isostructural tetrakis(2‐methoxyethyl)‐tetraaminoalkene ( 2b ) instantaneously reacted with O₂ to yield urea 3b , and silver nitrate was readily reduced with 2b to form a silver mirror. Compound 2a has been characterized by X‐ray diffraction studies; the naphtho‐pyrimidine skeleton imposes structural constraints and some rigidity to the CC bonding. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:82–87, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10088