Rhodiumkatalysierte enantioselektive 1,2‐Addition von Organoaluminiumverbindungen an cyclische Enone

Siewert, Jürgen; Sandmann, René; Zezschwitz, Paultheo von

doi:10.1002/ange.200701087

Cited by 16 publications

(11 citation statements)

References 34 publications

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“…Using the optimised reaction conditions, various cycloalk‐2‐enones with 5–7‐membered rings were converted into the corresponding tertiary allylic alcohols, all with ≥ 95 % ee (Table 3). The yields achieved when 0.5 mol % of the dimeric [{Rh(cod)Cl} 2 ] precursor and 1.5 mol % of AgBF 4 were used compare very well to yields previously obtained with 2.5 mol % of [{Rh(cod)OMe} 2 ] in the absence of silver salts 6. When 6‐membered rings are used as substrates yields are generally ≥ 80 %, with the single exception of a substrate with geminal disubstitution at the C5 position (Table 3, entry 3).…”

Section: Resultssupporting

confidence: 79%

“…This binap complex must be a precatalyst that slowly liberates the catalytically active species. Thus, we speculated that promoting the cleavage of this dimer would provide the key to a more active catalyst, even though we previously observed inferior results with [Rh(cod) 2 ]BF 4 as rhodium source 6. Fortunately, addition of a slight excess of AgBF 4 (based on the amount of chloride) led to a quantitative yield of the 1,2‐addition product 2 a with just 0.5 mol % of dimeric [{Rh(binap)Cl} 2 ].…”

Section: Resultsmentioning

confidence: 99%

“… [a] Isolated yield. Values in parentheses with 2.5 mol % [{Rh(cod)OMe} 2 ] without AgBF 4 6. [b] Determined by GC.…”

Section: Resultsmentioning

confidence: 99%

“…However, when using cycloalkenones as substrates, a substituent in the 2‐position is usually required to achieve high levels of selectivity 5f. g We have previously reported a Rh I /binap‐catalysed 1,2‐addition furnishing excellent levels of enantioselectity and high yields of product even in the case of unsubstituted cycloalkenones (Scheme ) 6. The utilisation of organoaluminium reagents as nucleophiles is an attractive feature of this method 7.…”

Section: Introductionmentioning

confidence: 99%

“…[5f, g] We have previously reported a Rh I /binap-catalysed 1,2-addition furnishing excellent levels of enantioselectity and high yields of product even in the case of unsubstituted cycloalkenones (Scheme 1). [6] The utilisation of organoaluminium reagents as nucleophiles is an attractive feature of this method. [7] Both inexpensive AlMe 3 and air-stable adduct DABCO-A C H T U N G T R E N N U N G (AlMe 3 ) 2 [8] (DABCO = 1,4-diazabicycloA C H T U N G T R E N N U N G [2.2.2]octane) can be used for the addition of a methyl group; aryl groups can be introduced from mixed alanes ArAlMe 2 .…”

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confidence: 99%

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Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2‐Addition of AlMe₃ to Enones

Kolb

Zuo

Siewert

et al. 2013

Chemistry A European J

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The development of an improved protocol for the enantioselective Rh(I) /binap-catalysed 1,2-addition of AlMe3 to cyclic enones is reported. (31)P NMR analysis of the reaction revealed that the catalyst in its resting state is a chloride-bridged dimer. This insight led to the use of AgBF4 as an additive for in situ activation of the dimeric precatalyst. Thus, the catalyst loading can now be reduced to only 1 mol% with respect to rhodium. Various 5-7-membered cyclic enones can be transformed into tertiary allylic alcohols with excellent levels of enantioselectivity and high yields. The obtained products are versatile synthetic building blocks, shown by a highly enantioselective formal total synthesis of the pheromone (-)-frontalin as well as formation of a bicyclic lactone that has the core structure of the natural flavour component "wine lactone".

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

“… [a] Isolated yield. Values in parentheses with 2.5 mol % [{Rh(cod)OMe} 2 ] without AgBF 4 6. [b] Determined by GC.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2‐Addition of AlMe₃ to Enones

Kolb

Zuo

Siewert

et al. 2013

Chemistry A European J

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Trimethylaluminum

Suzuki

Nagasawa

Saitō

et al. 2017

Encyclopedia of Reagents for Organic Synthesis

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Enantioselective Rhodium‐Catalyzed Addition of Arylboronic Acids to α‐Ketoesters

et al. 2008

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The transition-metal-catalyzed asymmetric addition of organometallic reagents to carbonyl compounds to produce enantiomer-enriched secondary or tertiary alcohols is a powerful tool for the construction of carbon-carbon bonds. Many organometallic reagents have been successfully used in this addition reaction.[1] However, a drawback for most organometallic reagents is their sensitivity to moisture and air, both of which impede the practical applications of these asymmetric carbon-carbon bond-forming reactions. As an exception, arylboronic acids are very stable to air and moisture. The catalytic enantioselective addition of arylboronic acids to carbonyl compounds has became a current focus for research, [1d] and a number of efficient chiral catalysts have been developed for the catalytic asymmetric addition of arylboronic acids to aldehydes [2] and aldimines.[3] However, the catalytic asymmetric addition of arylboronic acids to ketones, which are less active relative to aldehydes and aldimines, is more difficult, and only limited progress has been achieved. In 2006, Hayashi et al. reported the asymmetric addition of arylboronic acids to isatins, cyclic aketoamides, catalyzed by a rhodium/MeO-Mop (MeO-Mop = 2-methoxy-2'-diphenylphosphino-1,1'-binaphthyl) complex in high enantioselectivities (72-91 % ee).[4] By using a chiral phosphoramidite ligand derived from H 8 -binol (binol = 2,2'-dihydroxy-1,1'-binaphthyl), de Vries, Minnard, Feringa and et al. obtained 55 % ee in the same reaction.[5] The chiral phosphoramidite ligand was also used in the asymmetric addition of arylboronic acids to trifluoromethyl ketones with good enantioselectivities (50-83 % ee).[6] The intramolecular asymmetric addition of arylboronic acids to ketones catalyzed by a cationic palladium complex of binap (binap = 2,2'-bis(diphenylphosphanyl)-1,1'-binaphthyl) to give cyclic tertiary alcohols in high enantioselectivities (53-96 % ee) was reported by Lu et al. [7] To the best of our knowledge, the catalytic enantioselective addition of arylboronic acids to aketoesters to provide tertiary a-hydroxyesters has not yet been reported. [8] In the search for highly efficient methods to construct chiral 2-hydroxydiarylacetates, desirable chiral intermediates for the synthesis of antagonists of muscarinic receptors, [9] we became interested in the enantioselective addition of arylboronic acids to the a-aryl-and a-alkenyl-a-ketoesters. The Rh I /ShiP (ShiP = aryl(1,1'-spirobiindane-7,7'-diyl)phosphite) catalysts (1) recently developed by us [2c, 3b] were found to be highly efficient for this addition reaction to provide chiral tertiary a-hydroxyesters [10] in good yields and high enantiomeric excesses (up to 93 % ee).Preliminary experiments were carried out in H 2 O with catalyst generated in situ from 1.5 mol % [{RhCl-(CH 2 CH 2 ) 2 } 2 ][11] and 6 mol % (S)-1 a in the presence of two equivalents of LiF.[12] The addition of phenylboronic acid to ethyl 2-(4-chlorophenyl)-2-oxoacetate (2 a) at room temperature for 48 hours afforded tertiary a-hydroxyeste...

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Rhodiumkatalysierte enantioselektive 1,2‐Addition von Organoaluminiumverbindungen an cyclische Enone

Cited by 16 publications

References 34 publications

Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2‐Addition of AlMe₃ to Enones

Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2‐Addition of AlMe₃ to Enones

Trimethylaluminum

Enantioselective Rhodium‐Catalyzed Addition of Arylboronic Acids to α‐Ketoesters

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Rhodiumkatalysierte enantioselektive 1,2‐Addition von Organoaluminiumverbindungen an cyclische Enone

Cited by 16 publications

References 34 publications

Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2‐Addition of AlMe3 to Enones

Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2‐Addition of AlMe3 to Enones

Trimethylaluminum

Enantioselective Rhodium‐Catalyzed Addition of Arylboronic Acids to α‐Ketoesters

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Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2‐Addition of AlMe₃ to Enones

Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2‐Addition of AlMe₃ to Enones