Details
| Original language | English |
|---|---|
| Pages (from-to) | 2270-2280 |
| Number of pages | 11 |
| Journal | Chemistry - A European Journal |
| Volume | 5 |
| Issue number | 8 |
| Publication status | Published - 22 Jul 1999 |
| Externally published | Yes |
Abstract
Aldehydes are asymmetrically acylated by a two step sequence that is initiated by a homologation step to 1,1-heterodisubstituted alkenes followed by asymmetric dihydroxylation. Thus, ketene O,S-acetals are efficiently prepared from aldehydes by a Peterson olefination with lithiated methoxy-phenylthiotrimethylsilyl methane 14 as the C-1 source. Although they are dihydroxylated with the Sharpless catalyst with moderate to good enantioselectivity (62-80% ee), the process is not efficient owing to the low chemical yields of the desired α-hydroxy methyl esters (7-37%). Use of the corresponding sulfoxide 24 or sulfon 25 led to an improved chemical yield of α-hydroxy methyl ester 19, but the stereoselectivity was diminished. In contrast, intermediate ketene O,O-acetals are prepared by a Horner-Wittig reaction with phosphine oxide 31 and are dihydroxylated both with good chemical and stereochemical yield. The concept is applicable to aromatic, aliphatic, and chiral aldehydes. For example, this short sequence allows exclusive and independent preparation of both diastereomeric heptoses 69 a and 69 b.
Keywords
- Aldehydes, Asymmetric synthesis, C-C coupling, Dihydroxylations, Wittig reactions
ASJC Scopus subject areas
- Chemical Engineering(all)
- Catalysis
- Chemistry(all)
- Organic Chemistry
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In: Chemistry - A European Journal, Vol. 5, No. 8, 22.07.1999, p. 2270-2280.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Asymmetric nucleophilic acylation of aldehydes via 1,1-heterodisubstituted alkenes
AU - Monenschein, Holger
AU - Dräger, Gerald
AU - Jung, Alexander
AU - Kirschning, Andreas
PY - 1999/7/22
Y1 - 1999/7/22
N2 - Aldehydes are asymmetrically acylated by a two step sequence that is initiated by a homologation step to 1,1-heterodisubstituted alkenes followed by asymmetric dihydroxylation. Thus, ketene O,S-acetals are efficiently prepared from aldehydes by a Peterson olefination with lithiated methoxy-phenylthiotrimethylsilyl methane 14 as the C-1 source. Although they are dihydroxylated with the Sharpless catalyst with moderate to good enantioselectivity (62-80% ee), the process is not efficient owing to the low chemical yields of the desired α-hydroxy methyl esters (7-37%). Use of the corresponding sulfoxide 24 or sulfon 25 led to an improved chemical yield of α-hydroxy methyl ester 19, but the stereoselectivity was diminished. In contrast, intermediate ketene O,O-acetals are prepared by a Horner-Wittig reaction with phosphine oxide 31 and are dihydroxylated both with good chemical and stereochemical yield. The concept is applicable to aromatic, aliphatic, and chiral aldehydes. For example, this short sequence allows exclusive and independent preparation of both diastereomeric heptoses 69 a and 69 b.
AB - Aldehydes are asymmetrically acylated by a two step sequence that is initiated by a homologation step to 1,1-heterodisubstituted alkenes followed by asymmetric dihydroxylation. Thus, ketene O,S-acetals are efficiently prepared from aldehydes by a Peterson olefination with lithiated methoxy-phenylthiotrimethylsilyl methane 14 as the C-1 source. Although they are dihydroxylated with the Sharpless catalyst with moderate to good enantioselectivity (62-80% ee), the process is not efficient owing to the low chemical yields of the desired α-hydroxy methyl esters (7-37%). Use of the corresponding sulfoxide 24 or sulfon 25 led to an improved chemical yield of α-hydroxy methyl ester 19, but the stereoselectivity was diminished. In contrast, intermediate ketene O,O-acetals are prepared by a Horner-Wittig reaction with phosphine oxide 31 and are dihydroxylated both with good chemical and stereochemical yield. The concept is applicable to aromatic, aliphatic, and chiral aldehydes. For example, this short sequence allows exclusive and independent preparation of both diastereomeric heptoses 69 a and 69 b.
KW - Aldehydes
KW - Asymmetric synthesis
KW - C-C coupling
KW - Dihydroxylations
KW - Wittig reactions
UR - http://www.scopus.com/inward/record.url?scp=0040909104&partnerID=8YFLogxK
U2 - 10.1002/(SICI)1521-3765(19990802)5:8<2270::AID-CHEM2270>3.0.CO;2-L
DO - 10.1002/(SICI)1521-3765(19990802)5:8<2270::AID-CHEM2270>3.0.CO;2-L
M3 - Article
AN - SCOPUS:0040909104
VL - 5
SP - 2270
EP - 2280
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
IS - 8
ER -