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alpha,alpha'-Diactivated cyclic- or acyclic ketones undergo a chemoselective base promoted (K2CO3, DBU) one-pot C-C cycloalkylation, with 1,3- and 1,4-dihalides having a cis-like fixed configuration. This reaction gives highly functionalized bicyclo[3.2.1]octan-9-one and bicyclo[4.2.1]nonan-9-one derivatives, which are easily transformed to seven- and eight-membered rings through a high yield retro-Dieckmann cleavage. Starting from trans-1,4-dibromo-2-butenes, the transformation is governed by stereoelectronic factors and leads, through a chemo- and stereoselective C-O cycloalkylation, to synthetically valuable monocyclic or fused polycyclic functionalized enol ethers of high synthetic value. Semiempirical calculations showed a small difference in energy and the late character of the transition states leading to cis and trans isomers of the corresponding fused polycyclic enol ethers. These results, although minimizing the influence of a destabilizing 1,3-interaction on the outcome of the reaction, are qualitatively in agreement with the experimental results.

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Cyclic b-ketoesters and b-ketoamides undergo, in a onepot process, an unprecedented DBU-MeOH-promoted regio-and stereoselective g-functionalization with aldehydes, by a directed galdol reaction and dehydration sequence, to afford synthetically valuable alkylidene (or arylidene) cycloalkanones in good yields. While b-ketoesters give good results only with aromatic aldehydes, b-ketoamides react smoothly either with aromatic, aliphatic, or a,bunsaturated aldehydes following a totally regioselective 1,2-addition. The overall sequence, probably initiated by a reversible a-aldol reaction, allows the formation of hitherto unknown and stereodefined g-functionalized cycloalkanones having three reactive centers, such as two electrophilic and one nucleophilic site.Multifunctional reagents containing multiples different reactive sites constitute very important and valuable synthetic tools in organic synthesis, since they can be versatile intermediates for the selective construction of more complex structures found in natural and unnatural compounds. 1,3-Dicarbonyl derivatives, bearing both electrophilic and nucleophilic centers, constitute widely used examples which have found a broad spectrum of applications over the past 1 and still stimulate a large interest in modern synthetic organic chemistry. 2 Within this family, b-ketoesters 3 found widespread applications and recently, we have shown the usefulness of anionic domino transformations initiated by Michael addition to a,b-unsaturated aldehydes 4 using both the a-and g-reactive sites of cyclic and acyclic b-ketoesters. 5 However, in spite of the usefulness of these systems, their selective g-functionalization still remains a challenging problem. 6 In fact, whereas the directed g-alkylation of b-dicarbonyl derivatives through the corresponding dianions is well documented 7 and mainly referred as the Weiler alkylation, 8 the related selective g-alkylidenation via a regioselective aldol condensation-dehydration sequence has received little or no attention in the case of b-ketoamides. 9 Concerning acyclic b-ketoesters, the directed g-aldol type condensation 10 of dianions derived from acetoacetates, 11 combined with subsequent dehydration 12 or dehydrosulfenylation 13 and quation 1Downloaded by: University of Illinois at Chicago. Copyrighted material.