Stereoselective synthesis of cis-2-aryl- and 2-alkyl-1-chlorocyclopropanecarboxaldehydes

The Favorskii Rearrangement: Synthetic Applications

“…2-Substituted-1-chlorocyclopropanecarbaldehydes 162 (Scheme 54) have stereoselectively been synthesized via a semi-benzylic Favorskii rearrangement of boron 3-substituted-2,2-dichlorocyclobutanolates 161 [70]. It was not necessary to isolate the corresponding cyclobutanols.…”

Preparation of Novel 4′-Spirocyclopropyl Nucleoside Analogues

“…Several mechanistic studies have shown that the ringcontraction reaction of dichlorocyclobutanones proceeds by a semibenzilic Favorskii rearrangement, 9 promoted by subjecting the substrate to a reducing agent followed by base-promoted ring contraction of the intermediate alcohol in situ. 10 An evaluation of this protocol on the spirocyclic scaffold 10a (Scheme 1) gratifyingly resulted in a quantitative conversion into the intermediate dichlorocyclobutanol 10b, the structure of which was elucidated by NMR analysis. 11 Subsequently, an aqueous solution of NaOH was added to promote the in situ rearrangement of 10b through an 1,2-alkyl shift.…”

Highly Stereoselective Halocyclopropanation of α,β‐Unsaturated Amides

“…Thus, 1-chlorocyclopropanecarboxylic acids are precursors to a variety of aminocyclopropanecarboxylic acids known for their biological activity, [8] whereas 2-chlorocyclopro-A C H T U N G T R E N N U N G panecarboxylic acids are used to obtain agrochemical compounds, [9] and novel antitumour agents. [10] The chlorocyclopropane motif can be mainly accessed through the addition of carbenoids (SimmonsSmith-like process) [11] or carbene [12] species to double bonds; from a,a-dichloroalkyl anions (conjugated nucleophilic addition followed by a ring closing reaction), [13] from gem-dichlorocyclopropanes, [14] and by utilizing other starting materials such as 2,2-dichlorobutanols (Favorskii rearrangement), [15] carboalkoxychlorodiazirines, [16] or pyrazolines. [17] However, the majority of these methods present some drawbacks such as: a) the use of explosive, flammable or harmful reagents [12b-c,16] or those which are not readily available;…”

“…[11c,d,12c-d,13,14b-d, 15,16,17] In the case of bromocyclopropanation, to the best of our knowledge only one stereoselective synthesis of bromocyclopropanes has been reported via the bromination of cyclopropylindium reagents prepared from the allylindation of cyclopropenes which are not readily available. [18] The most employed method for the synthesis of bromocyclopropanes is based on the debromination of dibromocyclopropanes by using several reagents.…”