Preparation of neuroprotective condensed 1,4-benzoxazepines by regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction

• László Tóth,
• Yan Fu,
• Hai Yan Zhang,
• Attila Mándi,
• Katalin E. Kövér,
• Tünde-Zita Illyés,
• Attila Kiss-Szikszai,
• Balázs Balogh,
• Tibor Kurtán,
• Sándor Antus and
• Péter Mátyus

Beilstein J. Org. Chem. 2014, 10, 2594–2602, doi:10.3762/bjoc.10.272

• cellular injuries in human neuroblastoma SH-SY5Y cells in the range of those of positive controls. Keywords: 1,4-benzoxazepine; diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization; neuroprotective; tert-amino effect; TDDFT-ECD calculation; Introduction The 1,4-benzoxazepine structural

• functionalization in an internal redox process, particularly involving C–H bonds in α-position to a tertiary amine nitrogen atom, has attracted considerable attention due to its synthetic potential [7][8][9][10][11]. The intramolecular “tert-amino effect” induced cyclization consists in (1) the cleavage of the C

• (sp3)–H bond α to a tertiary amine nitrogen through [1,5]-hydride shift (rac-6→A) (Scheme 1) to afford the zwitterionic intermediate A and (2) subsequent 6-endo cyclization (A→rac-7a,b). The stereoselective version of “tert-amino effect” induced cyclization using chiral metal-catalyzed [12][13][14][15

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• transformations will not be covered in this review. Review Organocatalytic sp3 C–H bond activation reactions Non-asymmetric variants tert-Amino effect: The “tert-amino effect” refers to the ring-closure reactions that proceed by redox processes for C–C and C–X bond formation within conjugated systems [7][8][9

• ]. One well-known example of the “tert-amino effect” is the cyclization of N,N-dialkyl-substituted anilines with imines to generate cyclic aminals. The groups of Seidel and Akiyama independently reported mild organocatalytic approaches to cyclic aminals involving aminobenzaldehydes and primary amines [10

The tert- amino effect in heterocyclic chemistry: Synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives

• Dipak Prajapati and
• Kalyan Jyoti Borah

Beilstein J. Org. Chem. 2007, 3, No. 43, doi:10.1186/1860-5397-3-43

• pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives by exploring the α-cyclization of tertiary amine reaction strategy. The term tert-amino effect was coined by Meth-Cohn and Suschizky [8] to generalize cyclization reactions of certain ortho-substituted N,N-dialkylanilines. This effect has been observed in

• with at least one heteroatom, such as nitroso,[13] nitro,[14][15] azo,[16] amine,[17] azomethine, [18][19][20] carbonyl, [20][21][22][23] or thiocarbonyl moieties as the ortho substituents.[10] The application of the tert-amino effect to the synthesis of pyrido-fused benzenes, pyridazines and uracils

• Dipak Prajapati Kalyan Jyoti Borah Department of Medicinal Chemistry, North East Institute of Science & Technology (NEIST), Jorhat 785006, Assam, India 10.1186/1860-5397-3-43 Abstract The synthesis of novel fused heterocycles is based on reactions proceeding by the mechanism of the tert-amino