Convenient means of generating alkyl-substituted isobenzofurans as reactive intermediates

The Oxa‐Pictet–Spengler Reaction: A Highlight on the Different Efficiency between Isochroman and Phthalan or Homoisochroman Derivative Syntheses

“…Starting compounds are, for example, o-phthalyl alcohol [33][34][35][36][37] or o-phthalyl halides. [38][39][40][41][42][43] Figure 1. 1,3-Dihydroisobenzofuran.…”

“…Starting compounds are, for example, o-phthalyl alcohol [33][34][35][36][37] or o-phthalyl halides. [38][39][40][41][42][43] We synthesized hydroxyphthalans under the same conditions used for the synthesis of isochromans (see Experimental Section), but in some cases the temperature was increased to 38°C. We used 3-hydroxybenzyl alcohol (1), 3,5dihydroxybenzyl alcohol (2), and 3,5-dimethoxybenzyl alcohol (3) and a group of aromatic, as well as aliphatic, aldehydes chosen from those successfully used for the synthesis of isochromans.…”

Benz[f]isoindole

“…As expected, thermal decomposition of 2-naphthalenedi- (10), which reacted with 1 -(phenylmethyl)pyrrole to afford adduct 11. Hydrogenation of imine 11 in methanol in the presence of 10% palladium-charcoal gave ll-(phenylmethyl)-l,2,3,4-tetrahydroanthracen-l,4-imine (12). An attempt to convert 12 to compound 9 by selective hydrogenolysis failed; only 1,2,3,4-tetrahydroanthracene and benzylamine were recovered.…”

“…The apparatus used for flash vacuum thermolysis was modeled after that previously described. 13 11 -(Phenylmethyl)-1,4-dihydroanthracen-1,4-imine (11). A slurry of 2-naphthalenediazonium 3-carboxylate15 (1.35 g, 6.81 mmol) in 100 mL of dried 1,2-dimethoxy ethane was added in portions over a period of 30 min to a refluxing solution of 1-(phenylmethyl)pyrrole (2.13 g, 13.5 mmol) in 50 mL of 1,2-dimethoxyethane.…”

“…The mixture was shaken with hydrogen at 50 psi at room temperature for 2 h. The reaction mixture was filtered to remove catalyst and the filtrate was concentrated to yield 1.94 g (83.7%) of colorless crystals, mp 118-119 °C. Recrystallization from absolute methanol gave an analytical sample with melting point unchanged: NMR (CDCI3) 8.1 (m, 6 H, naphthyl), 5.6 (m, 2 H, bridgehead), 2.4 (m, 2 H, exo protons), and 1.5 (m, 11 H, endo and iert-butyl protons). Anal.…”