Asymmetric Hydroalkoxylation of Non‐Activated Alkenes: Titanium‐Catalyzed Cycloisomerization of Allylphenols at High Temperatures1. (3rd February 2015)

• Record Type: Journal Article
• Authors: Schlüter, Johannes; Blazejak, Max; Boeck, Florian; Hintermann, Lukas
• Is Part Of: Angewandte Chemie. Volume 127:Number 13(2015)
• Page Start: 4086
• Page End: 4089
• Publication Date: 2015-02-03
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201409252
• Languages: English
• ISSNs: 0044-8249

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The asymmetric catalytic addition of alcohols (phenols) to non‐activated alkenes has been realized through the cycloisomerization of 2‐allylphenols to 2‐methyl‐2, 3‐dihydrobenzofurans (2‐methylcoumarans). The reaction was catalyzed by a chiral titanium–carboxylate complex at uncommonly high temperatures for asymmetric catalytic reactions. The catalyst was generated by mixing titanium isopropoxide, the chiral ligand (<italic>aS</italic>)‐1‐(2‐methoxy‐1‐naphthyl)‐2‐naphthoic acid or its derivatives, and a co‐catalytic amount of water in a ratio of 1:1:1 (5 mol % each). This homogeneous thermal catalysis (HOT‐CAT) gave various (<italic>S</italic>)‐2‐methylcoumarans with yields of up to 90 % and in up to 85 % <italic>ee</italic> at 240 °C, and in 87 % <italic>ee</italic> at 220 °C.</p> </abstract>