Synthetic and structural studies in the [4.4.4.5]fenestrane series

Planar-Tetracoordinate Carbon in a Neutral Saturated Hydrocarbon: Theoretical Design and Characterization

“…In fact, the structure shows some correspondence to a synthetically known [4.4.4.5]fenestrane derivative that bears the most flattened tetracoordinate carbon atom (d 11.58) observed experimentally in an organic molecule to date. [18] The internal bonds to the central carbon atom in this fenestrane system are about 1.50 , while some peripheral bonds are as long as 1.60 .…”

100 Years of the Wolff Rearrangement

“…[332] The products 434 were used to develop gonadotropin-releasing hormone (GnRH) receptor antagonists 435. The ArndtϪEistert sequence was applied to (2R,3S)-3-acetoxyproline (436) in a synthesis of the GeissmanϪWaiss lactone 437, [333] a precursor of many pyrrolizidine alkaloids. A convergent synthesis of the cyclodepsipeptide (ϩ)-jasplakinolide was based on homologation of Boc-tyrosine-OTBDMS.…”

“…[443] Low-temperature photolysis of 606, followed by oxidation of the ketene intermediate to give the ring-contracted ketone 607, is an essential of the route to 608. Approaches to ''flattened'' quaternary carbon began with syntheses of tricyclo[4.2.0.0 1,4 ]octane [444] and its 6-methyl derivative [445] (609 Ǟ 610 Ǟ 611), went on to [4.4.5.5]fenestrane, [446] and culminated in derivatives of [4.4.4.5]fenestrane 613, R ϭ H [436] and OH. [447] The overall yields for the conversion of 612 into 613 (6% for R ϭ H and 13% for R ϭ OH) were much smaller than those for the less strained analogues, 609 Ǟ 610.…”

Recent advances in planar tetracoordinate carbon chemistry

“…The optimized geometry of C 5 2À at different levels of theory is shown in Figure 4 60 The experimental observation of any molecule is only possible if the molecule is stable for a certain detection period. Depending on the experimental technique of characterisation, the necessary detection time ranges from the microsecond scale to a couple of seconds.…”