Stereoselective synthesis of (3R*,3aS*,7aS*)-3-aryloctahydroindol-2-ones using radical cyclisation: a formal synthesis of (±)-pancracine

Phenylaziridine as a Masked 1,3 Dipole in Reactions with Nonactivated Alkenes

“…[10] The new chemical behavior of N-tosyl-2-phenylaziridine 1 is of interest from several points of view 1) in the presence of BF 3´E t 2 O the reactivity 1 with nonactivated olefins is equivalent to that of a 1,3 dipole, 2) molecular complexity is achieved in a single step, and 3) the obtained adducts are important precursors of biologically active molecules. Indeed the azabicycloadducts 3 a/4 a are valuable as strained phenylethylamines, [11] and are easily accessible from cheap starting materials, furthermore the production of spiropyrrolidines 10 ± 12 is of importance as this structural motive forms the core of some biologically active alkaloids. [12] Experimental Section General procedure for the reaction of 1 with alkenes: A solution of BF 3Ó Et 2 (0.06 mL, 0.5 mmol, 1 equiv) in CH 2 Cl 2 (0.3 mL) was added dropwise under argon to a solution of 1 (140 mg, 0.51 mmol) and alkene (1.4 equiv) in CH 2 Cl 2 (5 mL) cooled at À 78 8C.…”

The Synthesis of 9,10‐Dihydro‐9,10‐(Methaniminomethano)Anthracene andN‐Protected Derivatives Via Double Reductive Amination

“…[17 -19] Treatment of 2 with DDQ led only to decomposition. [20] However, reaction of 2 with benzyl chloroformate in refluxing benzene [21] gave the N-carbobenzyloxy (Cbz)-protected amine 3 in excellent yield (93%). The N-Cbz amine 3 could be converted to amine 1 by catalytic hydrogenation (H 2 -Pd/C) in 67% yield, or directly to the N-Boc derivative 4 in 79% yield when employing di-tert-butyl dicarbonate [22] in the reaction.…”

“…Complete spectral data have not previously been published for this compound. b IR (CH 2 Cl 2 ): 1793 (s) cm 21 cis-9,10-Dihydro-9,10-ethanoanthracene-11,12-diol (7). By a new procedure for this known compound, [7 -11,23] methanol (20 mL), THF (20 mL), and 3 M NaOH (20 mL) were added to cyclic carbonate 6 (1.37 g, 5.17 mmol) and the dispersion was stirred for 20 h at rt.…”

“…Complete spectral data have not previously been published for this compound. IR (CH 2 Cl 2 ): 2689 (w), 1722 (s) cm 21 (6). The known title compound (also known as cis-9,10-dihydro-9,10-ethanoanthracene-11,12-diol carbonate) was prepared from anthracene and vinylene carbonate according to the procedure of Murdock and coworkers, [7] except that five equivalents of vinylene carbonate were employed rather than 10 equivalents with no loss in yield.…”

“…No spectroscopic data have been previously published for this known [6] compound. R f ¼ 0.33 (50% ethyl acetate/ hexanes on neutral alumina, stained with I 2 ); IR (CH 2 Cl 2 ) 3351 (w) cm 21 12-(p-Methoxyphenyl)methyl)-9,10-dihydro-9,10-(methaniminomethano)anthracene (2). p-Methoxybenzylamine (58 mg, 0.42 mmol) and acetic acid (25 mg, 0.42 mmol) were dissolved in CH 2 Cl 2 (4 mL) and cooled to 2788C.…”