“…A series of 1,2-bis(TMS)allylic alcohols (see Scheme and Table ), were prepared via the reaction of 7 with the required aldehydes. We next considered a proposed allenylation by sequential Brook and Peterson transformations. It was found that the use of n -BuLi, per se, did not accomplish the desired allenylation.…”
A mild and efficient two-carbon homologation of aldehydes exploiting multiple modes of KOt-Bu was developed. This process involves a sequential Peterson allenylation/allene-alkyne isomerization/ protodesilylation in a single-flask operation. The differential roles played by the various elements of the process were demonstrated through dissection experiments.
“…A series of 1,2-bis(TMS)allylic alcohols (see Scheme and Table ), were prepared via the reaction of 7 with the required aldehydes. We next considered a proposed allenylation by sequential Brook and Peterson transformations. It was found that the use of n -BuLi, per se, did not accomplish the desired allenylation.…”
A mild and efficient two-carbon homologation of aldehydes exploiting multiple modes of KOt-Bu was developed. This process involves a sequential Peterson allenylation/allene-alkyne isomerization/ protodesilylation in a single-flask operation. The differential roles played by the various elements of the process were demonstrated through dissection experiments.
“…But when the reaction mixture was quenched with a proton source, the expected 38 was not formed; instead the cyclized product 39 was obtained, which contained the three rings of the right-hand side of the desired ring system (vide supra). We felt that this reaction, thought to be driven by migration of the TIPS and then elimination of TIPSO - ( 40 → 41 ), could be utilized if the key intermediate 42 could be synthesized. 4 Carbon−Carbon Bond Formation via Metal−Halogen Exchange…”
[reaction: see text] The total synthesis of HKI 0231B (1b) was completed in 12 linear steps and 15.6% overall yield. An unusual anionic cyclization provided access to intermediate 61 and the embedded benz[cd]indol-3-(1H)-one ring system 3. Directed ortho-lithiation in the presence of a ketone followed by formylation and finally acid-catalyzed methanolysis complete the synthesis. Studies directed toward the construction and reactivity of the lactam acetal functionality present in HKI 0231A (1a) are also reported.
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