Heteroatom Chemistry Volume 14, Number 1, 2003 1,1 ′ ,3,3 ′ -Tetraalkyl-2,2 ′ -biperimidinylidenes: Unexpected Substituent Effects on the Reactivity of Carbon–Carbon Double Bond B¨ ulent Alıcı, 1 Tuncer H¨ okelek, 2 Engin C ¸ etinkaya, 3 and Bekir C ¸ etinkaya 3 1 Department of Chemistry, ˙ In¨ on ¨ u University, 44069 Malatya, Turkey 2 Department of Physics, Hacettepe University, 06532 Beytepe-Ankara, Turkey 3 Department of Chemistry, Ege University, 35100 Bornova-Izmir, Turkey Received 11 April 2002; revised 7 May 2002 ABSTRACT: C 2 deprotonation of 1,3-dibutylperimi- dinium bromide (1a) with sodium hydride and a cat- alytic amount of potassium tert-butoxide in dry THF led to the formation of the exceptionally inert tetraa- minoalkene 2a. In contrast, isostructural tetrakis(2- methoxyethyl)-tetraaminoalkene (2b) instantaneously reacted with O 2 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 diffrac- tion studies; the naphtho-pyrimidine skeleton imposes structural constraints and some rigidity to the C C bonding. C  2003 Wiley Periodicals, Inc. Heteroatom Chem 14:82–87, 2003; Published online in Wiley Inter- Science (www.interscience.wiley.com). DOI 10.1002/hc. 10088 INTRODUCTION Exobicylic enetetramines of the type [ : CN(R)ANR] 2 (R = primary alkyl; A = CH 2 CH 2 , CH 2 CH 2 CH 2 , Correspondence to: Bekir C ¸ etinkaya; Department of Chem- istry, Ege University, 35100 Bornova-Izmir, Turkey; e-mail: bekircetinkaya@hotmail.com. Contract grant sponsor: Scientific and Technical Research Council of Turkey. Contract grant number: DPT/TBAG1. Contract grant sponsor: State Planning Organization. Contract grant number: 98-DPT-001. c  2003 Wiley Periodicals, Inc. or C 6 H 4 -o) are strongly nucleophilic and highly reactive [1–3]. Electrophiles such as dioxygen and HX induce scission of the formal C C bond (e.g., chemiluminescent behavior) and is typical of N- alkyl enetetramines [4]. In this context, a number of carbene complexes have been prepared by the reaction of enetetramines with coordinatively unsat- urated transition metal complexes by cleavage of the carbon–carbon bond [5]. The preparation of such carbene complexes from enetetramines has a close analogy with that of tertiary phosphine complexes from PR 3 . Some of the carbene complexes, L n M- CN(R)ANR, have been found to be good catalysts for a variety of transformations [6–10]. Therefore, we were interested in synthesizing and exploring the chemistry of the hitherto unknown naphtho-fused alkenes 2. The use of a naphtho-fused pyrimidine skeleton was expected to enhance the rigidity of the derived compounds. EXPERIMENTAL Reagents and Techniques All manipulations of air- and/or moisture-sensitive compounds were carried out under an argon atmo- sphere by using standard Schlenk techniques. Sol- vents were dried and freshly distilled under argon be- fore use. IR absorption spectra were obtained from 82