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

作者：Clark Andrew J; Cornia Andrea; Felluga Fulvia; Gennaro Armando; Ghelfi Franco^*; Isse Abdirisak A; Menziani Maria Cristina; Muniz Miranda Francesco; Roncaglia Fabrizio; Spinelli Domenico

来源：European Journal of Organic Chemistry, 2014, 2014(30): 6734-6745.

DOI：10.1002/ejoc.201402769

• Protecting groups
• Deprotection
• Lactams
• Radicals
• Cyclization
• Amides

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--polychloroamides, can be effectively removed from the target -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.

• 出版日期2014-10