Inductive enhancement of aryl participation

The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

“…Heating the corresponding alkyl halide (Br or I) with PPh 3 under reflux in concentrated solutions of toluene, benzene, or acetonitrile gave phosphonium salts 7a –7 c and 7e . Starting from 4-chlorophenylacetic acid, 4-chlorophenethyl bromide ( 8 ) was prepared in 78% overall yield according to the literature method [ 48 ] ( Scheme 9 ). The phosphonium salt 7c , an intermediate to dibromide 1c , was prepared starting from the known 2-( trans -4-pentylcyclohexyl)acetaldehyde ( 9 ) [ 49 ].…”

Increased electron demand in the solvolysis of secondary 2-norbornyl tosylates

“…15 Experimental Section Spectral, kinetic, and other instrumental equipment has been described earlier.3 c/s,exo-2,3-Norbornyl ditosylate (5, X = OTs) was available from our earlier study.2 c/s,eui/o-2,3-Norborn-5-enyl carbonate. The Diels-Alder reaction was carried out as described by Kwart and by Newman.16 A solution of 8.15 g (0.095 mol) of vinylene carbonate (Aldrich) and 6.5 g (0.049 mol) of freshly distilled dicyclopentadiene (Eastman) in 32 mL of benzene was sealed in a Pyrex tube, which was heated at 200 °C for 8 h. The tube was opened and the solvent removed by vacuum distillation to give a brown solid, which was dissolved in ether, decolorized with activated charcoal, and finally recrystallized from ether/hexane to give 12.32 g (86%) of the desired compound: NMR (CDCfl) 1.25 (d, 1 ), 1.75 (d of t, 1 H), 3.25 (m, 2 H), 4.96 (t, 2 ), 6.17 (t, 2 H).…”

“…The carbonate was reduced by treatment with 1.25 g (0.0328 mol) of L1AIH4 in ether. Treatment of the alkoxide with NaOH solution and removal of the solvent gave 3.12 g (82%) of the diol after recrystallization from acetone/hexane: mp 209-211 °C; NMR (CCI4) 1.14 (m, 4 ), 1.70 (m, 2 H), 2.25 (br s, 2 H), 3.76 (br s, 2 ), 4.03 (br s, 2 H). Anal.…”

“…When Ar = P-CH3C6H4, the increase is from 66 to 99%. 3 The electron-withdrawing X group (OTs or OAc) destabilizes the development of positive charge in the transition state. Electron demand at the 2 position is thereby increased (compared with the case when X is H), and the system has a greater need for participation.…”

Wortmannines A–C, three novel wortmannin derivatives with an unusual five-membered B ring from the endophytic fungus Talaromyces wortmannii LGT-4

“…As a result, we chose the corn solid culture medium to continue our work which resulted in the isolation of three novel wortmannin scaffold derivatives (wortmannines A-C, 1-3) and a 4-methyl substituted androstadiene-17-one (wortmannine D, 4). In addition, four known compounds, entonaemin A (5), 9 meso-1,4-bis(4-methoxyphenyl)-2,3-butanediol (6), 10 and monomethylsulochrin (7), 11 (4S,4aS,5R,6aS,9aR)-5-(acetyloxy)-1-(aminomethylene)-4,4a,5,6,6a,8,9,9a-octahydro-11-hydroxy-4-(methoxy methyl)-4a,6a-dimethyl-cyclopenta [5,6]naphthol [1,2-c] pyran-2,7,10(1H)-trione (8), 12 were also isolated during the purification process. This paper describes the isolation, structure elucidation, and biological activity of these compounds.…”