Rotanes synthesis

A short paper, the beginning of whose title is designed to catch the eye, A universal rotane synthesis announced the synthesis of [6]rotane 85 for the first time via carbene addition to 84, 1). An alternative method was to add carbene to a starting material 86, containing two double bonds 32. ... 

The syntheses of [4], [5], and [6]rotanes as well as precursors for those of [7] and [8]-rotanes have been recorded in a full paper 34. In another synthetic study of rotane synthesis employing ring enlargement of certain ketonic intermediates, led perhaps by design, perhaps with the intervention of serendipity, to compounds such as 88 35. ... 

The Simmons-Smith reaction is well suited for the synthesis of spirocyclic compounds. It has for example been applied for the construction of the fifth cyclopropane ring in the last step of a synthesis of the rotane 8 ... 

Scheme 31. Attempted synthesis of spirocyclopropanated butadiyne-expanded [n]rotanes from the acyclic precursors 150 and 151...

Acetylene- and Diacetylene-Expanded Cycloalkanes and Rotanes. 201 1 -42 de Meijere A, Kozhushkov SI, Khlebnikov AF (2000) Bicyclopropylidene - A Unique Tetra-substituted Alkene and a Versatile Cj-Building Block. 207 89-147 de Meijere A, Kozhushkov SI, Hadjiaraoglou LP (2000) Alkyl 2-Chloro-2-cyclopropylidene-acetates - Remarkably Versatile Building Blocks for Organic Synthesis. 207 149-227 Dennig J (2003) Gene Transfer in Eukaryotic Cells Using Activated Dendrimers. 228 227-236 de Raadt A, Fechter MH (2001) Miscellaneous. 215 327-345 Desreux JF, see Jacques V (2002) 221 123-164... 

One exception as to the previous sentence is the synthesis of [4]rotane by thermal dimerization of bicyclopropylidene 79 25). 

Apparently Fitjer likes to work with p-TsOH in aqueous acetone. Since as of the day of the destruction of the Temple, prophecy has been withdrawn from the prophets and has been given to fools and to babes 43 I shall not prophecy but I shall hazard a prediction. I belive that there are acidic conditions, yet to be found experimentally, which will permit the synthesis of beautiful molecules, by malice aforethought, such as, say, 99, from the properly constituted derivatives of certain rotanes and their homologs. May Fitjer be successful in his quest for [m.njcoronanes but it behooves him, simultaneously, to seek optimal conditions for the preparation of, say, 99 and its propellane homologs. I would even settle for 100 or 101 ... 

Rotane was first synthesized by Rippol and Conia29. The key steps included the synthesis of dispirononanone 13 (equation 11). Condensation of 13 with formaldehyde provided the tetrahydroxymethyl derivative 32, which was converted into the tetraspiro compound 33 by tosylation-bromination followed by reductive cyclization. Subsequent Wittig methylenation and cyclopropanation of the ketone 33 completed the synthesis (equation 30). 

An analogous procedure was employed in the synthesis of the perspirocyclopropanated [3]-rotane, e.g. 6, by addition of diazo[7]triangulane, generated in situ, to bicyclopropylidene. The precursor TV-nitrosourea was reacted with ten equivalents of sodium methoxide at 0 C in the presence of an excess of bicyclopropylidene and the perspirocyclopropanated [3]rotane formed was separated from the allene side product by column chromatography. 

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