Highly Regio‐ and Diastereoselective Chromium(0)‐Catalysed Cyclopropanation of 1‐Alkoxy‐1,3‐dienes with Diazo Compounds

Abstract

Pentacarbonyl(η 2 -cis-cyclooctene)chromium(0) (1) is an efficient catalyst for diazo decomposition and selective [2+1]-cycloaddition reactions of the resulting carbene intermediates with electron-rich dienes. The cyclopropanation of 1-alkoxy-1,3-butadienes 4−8 with 9-diazo-9H-fluorene (2) yields vinylspirocyclopropanes 9−13 in good to excellent yields, as single regioisomers arising from carbene transfer to

Efficient and regioselective chromium(0)-catalyzed reaction of 2-substituted furans with diazo compounds: stereoselective synthesis of (2E,4Z)-2-aryl-hexadienedioic acid diesters

“…General procedure for the preparation of ethyl adiazoarylacetates 1,.0]undec-7-ene (DBU) (4.1 ml, 27.5 mmol) in THF (20 ml) was added to a solution of the ethyl arylacetate (25 mmol) and p-acetamidobenzenesulfonylazide (p-ABSA) [22] (6.61 g, 27.5 mmol) in THF (50 ml) over 1 h at room temperature. The reaction mixture was stirred for an additional 12 h, then quenched by addition of saturated aqueous ammonium chloride (50 ml).…”

“…Pentacarbonylchromium(0) fragments also catalyze the reaction of electron-rich olefins and electron-rich dienes with diazo compounds [1,12]. In this paper, we present a detailed study of the pentacarbonylchromium(0)-catalyzed reaction of diazo compounds with electron-rich furans which has been addressed only in rare examples, so far [6,11].…”

“…R f = 0.47(el- uent: petroleum ether/diethyl ether, 8:1). IR (KBr): m = 3080 cm À1 (w, C-H), 2985 cm À1 (m, C-H), 2096 cm À1 (s, C‚N 2 ), 1697 cm À1 (s, C‚O) 1. H NMR (400 MHz, C 6 D 6 ): d = 0.94 (t, 3H, 3 J HH = 7.1 Hz, CH 3 ), 3.99 (q, 2H, 3 J HH = 7.1 Hz, O-CH 2 ), 7.14 (d, 2H, 3 J HH = 8À CO].…”