The N-arylsulfonyl group, which is the best and most useful cyclization auxiliary for the transition-metal-catalyzed atom transfer radical cyclization (ATRC) of N-allyl-α-polychloroamides, can be effectively removed from the target γ-lactams by using H2SO4–HOAc, without impairing the halogen functions. The reaction involves H+ attack on the aromatic moiety, and is strongly responsive to the electronic properties of the substituent bound to the aromatic ring: electron-donating groups, such as methyl or methoxy are, in fact, required for efficient “deprotection”. The N-p-nitrophenylsulfonyl cyclization auxiliary, in contrast to all the other sulfonyl groups tested, proved to be unsuitable for the ATRC, owing to a side reductive transposition that halts the redox cycle

Arylsulfonyl Groups: The Best Cyclization Auxiliaries for the Preparation of ATRC γ-Lactams can be Acidolytically Removed

FELLUGA, FULVIA;
2014-01-01

Abstract

The N-arylsulfonyl group, which is the best and most useful cyclization auxiliary for the transition-metal-catalyzed atom transfer radical cyclization (ATRC) of N-allyl-α-polychloroamides, can be effectively removed from the target γ-lactams by using H2SO4–HOAc, without impairing the halogen functions. The reaction involves H+ attack on the aromatic moiety, and is strongly responsive to the electronic properties of the substituent bound to the aromatic ring: electron-donating groups, such as methyl or methoxy are, in fact, required for efficient “deprotection”. The N-p-nitrophenylsulfonyl cyclization auxiliary, in contrast to all the other sulfonyl groups tested, proved to be unsuitable for the ATRC, owing to a side reductive transposition that halts the redox cycle
2014
http://onlinelibrary.wiley.com/doi/10.1002/ejoc.201402769/abstract;jsessionid=3B58123F74D61C83C76EC79CD1DE3026.f03t03?systemMessage=Wiley+Online+Library+will+be+disrupted+on+the+18th+October+from+10%3A00+BST+%2805%3A00+EDT%29+for+essential+maintenance+for+approximately+two+hours+as+we+make+upgrades+to+improve+our+services+to+you
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2809534
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