Doering-Moore-Skattebol method

The Doering-Moore-Skattebol method including a cyclopropylidene-allene rearrangement is often used for the synthesis of allenes. However, the reaction conditions applied are often not compatible with acceptor substituents. One of the rare exceptions is the transformation 76 —> 77 (Scheme 7.11) [122]. The oximes 77 are not accessible by the classical route starting from allenyl ketone and hydroxylamine (see Section 7.3.2). 

Cyclohexa-1,2-diene (76) generated in this way can be trapped with styrene, - hexa-2,4-diene, 2,3-dimethylbuta-1,3-diene, cyclopenta-1,3-diene, furan and 2-methylfuran to give [2 - - 2] cyclo-adducts and the product distribution was independent of the mode of preparation. 1-Methylcyclohexa-1,2-diene (79), also prepared by the Doering-Moore-Skattebol method, readily dimerized to give 80 and formed [2 - - 2] cycloadducts with styrene (81). ... 

Stable nine-membered rings or higher homologs of endocyclic allenes are routinely prepared by the Doering-Moore-Skattebol method (Table 6). 

Bis-allenes can be prepared by the Doering-Moore-Skattebol method from bisfdibromocyclo-propyl) derivatives, e.g. 136 ° and 141. ° These reactions appear to proceed by a stepwise rather than a one-step mechanism as evident from byproducts which are derived from intermediate cyclopropylideneallenes via intramolecular insertion processes (C-H or double bond insertions). These reactions often predominate to the exclusion of bis-allene formation, e. g. in the case of 139. °°... 

Conjugated bis-allenes separated by vinyl, aryl or heteroatomic groups can be prepared from their corresponding bisdihalocyclopropanes by the Doering-Moore-Skattebol method. However, competing processes such as the Skattebol rearrangement and other intramolecular processes often represent predominant pathways, for example, reactions of 157 and 159 further examples can be found in refs 116-120. 

Cumulenes can be prepared by the Doering-Moore-Skattebol method using methylene-substituted dihalocyclopropanes. In principle, such reactions can be used in succession to produce extended cumulenes however, limitations include the stability of the cumulene and the non-regioselectivity of the carbene insertion reactions. 

At temperatures above —100 °C the lithiohalocyclopropanes are converted to cyclopropylidenes by formal loss of one molecule of lithium halide. The main route of stabilization of these carbenacyclopropanes consists in the formation of allenes. The process which has been termed the Doering-Moore-Skattebol allene synthesis ( DMS-synthesis ) [66-68], has been developed into the most general method for the preparation of these reactive compounds which especially during the last decade have been used in organic synthesis with growing success [69, 70],... 

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