Highly Concentrated Catalytic Asymmetric Allylation of Ketones

Abstract

[reaction: see text] We report the catalytic asymmetric allylation of ketones under highly concentrated reaction conditions with a catalyst generated from titanium tetraisopropoxide and BINOL (1:2 ratio) in the presence of isopropanol. This catalyst promotes the addition of tetraallylstannane to a variety of ketones to produce tertiary homoallylic alcohols in excellent yield (80-99%) with high enantioselectivities (79-95%). The resulting homoallylic alcohols can also be epoxidized in situ using tert-butyl hydroperoxide (TBHP) to afford cyclic epoxy alcohols in high yield (84-87%).

Chemoselective Allylation of Ketones in Ionic Liquids Containing Sulfonate Anions

“…Allylation of levoglucosenone 2 f with tetraallyltin 1 in BMIm-BF 4 with recycling of solvent: 2 f (42 mg, 0.33 mmol) was dissolved in BMIm-BF 4 ( 0.3 mL) and stirred for few minutes at room temperature. 1 (0.019 mL, 0.08 mmol) was added followed by TfOH (2.6 mL, 0.03 mmol).…”

“…Exploiting the above described features, the most successful application of tetraallyltin, discovered by Tagliavini [2a] and improved by Walsh, [2b-d] is the enantioselective allylation of ketones catalyzed by binapthol(BINOL)-Ti complexes, [3] usually carried out in dichloromethane. An interesting version of this asymmetric catalytic methodology in highly concentrated isopropanol solution has been recently developed by Walsh; [4] however, dichloromethane is also required for the preparation of the catalyst.…”

“…The best reaction media are RTIL: N-methyl-N-butylpyrrolidinium trifluoromethansulfonate (MBPTf) or 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF 4 ) containing 10 % mole of trifluoromethanesulfonic acid (TfOH). Methanesulfonic acid (MsOH) or 4-methylbenzensulfonic acids (TsOH) can effectively substitute TfOH in this combination and other ionic liquids can be used instead of BMIm-BF 4 . Although less efficient, the combination of molecular organic solvents (chloroform, dichloromethane, acetonitrile) and a sulfonic acid can perform the allylation reaction.…”

A Green Chemistry Approach to Asymmetric Catalysis: Solvent-Free and Highly Concentrated Reactions

“…223 Thus, Wooten, Kim and Walsh conducted the asymmetric allylation of enones under highly concentrated conditions followed by a chemo-and diastereoselective directed epoxidation of the allylic double bond (Table 38). 221 In this reaction, the titanium allylation catalyst also catalyzes the diastereoselective directed epoxidation reaction. In this way, the ketone allylation under highly concentrated conditions was followed by addition of 1 equiv of anhydrous TBHP (5.5 M) ( Table 38).…”

tert-Butyl Hydroperoxide (TBHP): A Versatile Oxidizing Agent in Organic Synthesis

“…12 The epoxides have been obtained in good yields and with ee values of 80-90%. 13 (D) Manganese(III) acetate catalyzed allylic oxidation of alkenes to the corresponding enones was investigated and showed excellent regioselectivity. 14 Some new strategies have been reported for a useful transformation of the allylic oxidation of alkenes to carbonyl compounds, such as the protocols using TBHP catalyzed by transition-metal ion centers (Cr, Ru, Cu, Co, Pd).…”