title: Unsaturated Four-Membered Rings: Efficient Strategies for the Construction of Cyclobutenes and Alkylidenecyclobutanes.
abstract: Our recent studies of the diastereo- and enantioselective formation of strained alkylidenecycloalkanes drove us to more-thoroughly investigate the formation of four-membered rings for which only few efficient methods are described. We first developed a strategy to diversify the saturated part of the four-membered ring and applied it to a highly diastereoselective synthesis of more-elaborate alkylidenecyclobutanes, which completed our precedent studies. In parallel, cyclobutene structures were built employing simple organometallic methods and further functionalized to give a diverse range of new substitution patterns, which consequently enriched the pool of cyclobutene-based building blocks.
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig-Maximilians University of Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Eisold
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig-Maximilians University of Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
authors.forename: Andreas N
authors.initials: AN
authors.lastname: Baumann
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig-Maximilians University of Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Kiefl
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig-Maximilians University of Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
authors.forename: Sebastian T
authors.initials: ST
authors.lastname: Emmerling
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig-Maximilians University of Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
authors.forename: Dorian
authors.identifier: http://orcid.org/0000-0002-6358-1485
authors.initials: D
authors.lastname: Didier
keywords: alkylidenecyclobutanes; allylboration; boron; cross-coupling; cyclobutenes