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Controlled Rearrangement of Lactam‐Tethered Allenols with Brominating Reagents: A Combined Experimental and Theoretical Study on α‐ versus β‐Keto Lactam Formation
Author(s) -
Alcaide Benito,
Almendros Pedro,
Luna Amparo,
Cembellín Sara,
Arnó Manuel,
Domingo Luis R.
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201101160
Subject(s) - lactam , chemistry , reagent , adduct , cleavage (geology) , ring (chemistry) , stereochemistry , bond cleavage , organic chemistry , catalysis , fracture (geology) , geotechnical engineering , engineering
Abstract N ‐Bromosuccinimide (NBS) smoothly promotes the ring expansion of lactam‐tethered allenols to efficiently afford cyclic α‐ or β‐ketoamides with good yields and high chemo‐, regio‐, and diastereoselectivity, through controlled CC bond cleavage of the β‐ or γ‐lactam nucleus. Interestingly, in contrast to the rearrangement reactions of 2‐azetidinone‐tethered allenols, which lead to the corresponding tetramic acid derivatives (β‐keto lactam adducts) as the sole products, the reactions of 2‐indolinone‐tethered allenols under similar conditions give quinoline‐2,3‐diones (α‐keto lactam adducts) as the exclusive or major products. To rationalize the experimental observations, theoretical studies have been performed.