Arylsulfonyl Groups: The Best Cyclization Auxiliaries for the Preparation of ATRC γ‐Lactams can be Acidolytically Removed. Issue 30 (12th September 2014)

• Record Type: Journal Article
• Authors: Clark, Andrew J.; Cornia, Andrea; Felluga, Fulvia; Gennaro, Armando; Ghelfi, Franco; Isse, Abdirisak A.; Menziani, Maria Cristina; Muniz‐Miranda, Francesco; Roncaglia, Fabrizio; Spinelli, Domenico
• Is Part Of: European journal of organic chemistry. Issue 30(2014)
• Page Start: 6734
• Page End: 6745
• Publication Date: 2014-09-12
• Subjects: Protecting groups -- Deprotection -- Lactams -- Radicals -- Cyclization -- Amides; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201402769
• Languages: English
• ISSNs: 1434-193X

Abstract

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 H2 SO4 –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. Abstract : Acid removal of arylsulfonyl groups, which are the best and most useful cyclization auxiliaries for the transition‐metal‐catalyzed atom transfer radical cyclization (ATRC) of N ‐allyl‐α‐polychloroamides, can be effectively performed by using H2 SO4 in HOAc, but the aromatic ring needs to be "electron rich".