Chemoselective Carbonyl Allylations with Alkoxyallylsiletanes

Abstract

Alkoxyallylsiletanes are capable of highly chemo-and diastereoselective carbonyl allylsilylations. Reactive substrates include salicylaldehydes and glyoxylic acids. Chemoselectivity in these reactions is thought to arise from a mechanism involving first exchange of the alkyoxy group on silicon with a substrate hydroxyl followed by activation of a nearby carbonyl by the Lewis acidic siletane and intramolecular allylation. In this way, substrates containing multiple reactive carbonyl groups (e.g. dialdehyde or triketone) can be selectively monoallylated, even overcoming inherent electrophilicity bias (e.g. nucleophilic addition to a ketone in the presence of an aldehyde).

Characterization of Leptazolines A–D, Polar Oxazolines from the Cyanobacterium Leptolyngbya sp., Reveals a Glitch with the “Willoughby–Hoye” Scripts for Calculating NMR Chemical Shifts

“…This simple glitch in the original script calls into question the conclusions of a significant number of papers on a wide range of topics in a way that cannot be easily resolved from published information because the operating system is rarely mentioned. In the first half of 2019 alone, the protocol was referenced/used during the elucidation of several natural products, − to characterize reaction products, ,, and to understand biosynthetic pathways . Authors who used these scripts should certainly double-check their results and any relevant conclusions using the modified scripts in the SI.…”

Recent advances in the reactions of silacyclobutanes and their applications

“…In 2019, O'Neil and coworkers reported a chemoselective carbonyl allylation between alkoxyallylsiletanes and salicylaldehydes (or glyoxylic acids) under heating conditions (Scheme 24). 48 DFT calculations coupled with previous reports 49 suggested that the electron-rich oxygen atom played an integral role in stabilizing the transition state during the process, leading to the final product. Additionally, the robustness of this methodology was demonstrated as well with excellent enantioselectivity and good yields by late-stage modification of some natural products and drug molecules.…”

Towards Knowledge Maintenance in Scientific Digital Libraries with the Keystone Framework

“…Support conformational analysis [9,22] "Conformational analysis of 4 was performed with Schrödinger MacroModel 2016 by following the method of Willoughby et al [35]." Successful example [53] "The successful characterization of karlotoxin 2 (KmTx2) followed by KmTx8 [17,28,33,40] "Therefore, we turned to a protocol that relies on density functional theory-based computations of 1H and 13C NMR chemical shifts and the use of statistical tools to assign the experimental data to the correct isomer of a compound [28]. "…”

“…The remaining four papers [17,28,33,40] stated that they used the WH protocol to calculate the theoretical NMR chemical shift and thus could be significantly impacted, because the theoretical NMR chemical shifts supported findings that went into abstracts or the conclusion section. We say "could be" because the nonreproducibility comes from the protocol's implementation rather than the protocol itself.…”