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Herein reported is a strategy for constructing vicinal 4°/3° carbons via reductive Cope rearrangement. Substrates have been designed which exhibit Cope rearrangement kinetic barriers of ∼23 kcal mol −1 with isoenergetic favorability (Δ G ∼ 0). These fluxional/shape-shifting molecules can be driven forward by chemoselective reduction to useful polyfunctionalized building blocks.
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The aromatic Claisen rearrangement of a 1,2-azaborine
The first aromatic Claisen rearrangement of a 1,2-azaborine is described along with a quantitative kinetic comparison of the reaction of the azaborine with its direct all-carbon analogue. The azaborine A rearranged in a clean, regioselective fashion and reacted faster than the all-carbon substrate B at all temperatures from 140–180 °C. Activation free energies were extracted from observed first-order rate constants (A: Δ G ‡298K = 32.7 kcal mol −1 ; B: Δ G ‡298K = 34.8 kcal mol −1 ) corresponding to a twenty fold faster rate for A at observed reaction temperatures. DFT calculations show that the rearrangement proceeds via a concerted six-membered transition state and that the electronic structure of the BN and CC rings is mostly responsible for the observed regioselectivity and relative reactivity.
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- Award ID(s):
- 2117246
- PAR ID:
- 10413476
- Date Published:
- Journal Name:
- Organic & Biomolecular Chemistry
- Volume:
- 21
- Issue:
- 18
- ISSN:
- 1477-0520
- Page Range / eLocation ID:
- 3778 to 3783
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d2ob02186b
