1995
DOI: 10.1021/ja00142a042
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Double stereodifferentiating Lewis acid-promoted (Mukaiyama) aldol bond constructions.

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Cited by 57 publications
(41 citation statements)
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“…[22a, 28, 29] Indeed, enolsilane 23, derived from 5 and fragment 4, coupled to give the Felkin diastereomer 24 as the major product. Comparison of coupling constants (J 8-H,9-H = 9.8 Hz, J 9-H,10-H = 1.4 Hz) with those of structurally related compounds [27] revealed an anti configuration at C8-C9. Mild deoxygenation involving treatment with NaHMDS in CS 2 and MeI, [30] reduction of the xanthogenate with Bu 3 SnH·Et 3 B, [31] and subsequent deprotection with DDQ [32] provided primary alcohol 25 in 78 % yield over three steps.…”
Section: Scheme 2 Retrosynthesis Of Gephyronic Acid (3)mentioning
confidence: 96%
See 1 more Smart Citation
“…[22a, 28, 29] Indeed, enolsilane 23, derived from 5 and fragment 4, coupled to give the Felkin diastereomer 24 as the major product. Comparison of coupling constants (J 8-H,9-H = 9.8 Hz, J 9-H,10-H = 1.4 Hz) with those of structurally related compounds [27] revealed an anti configuration at C8-C9. Mild deoxygenation involving treatment with NaHMDS in CS 2 and MeI, [30] reduction of the xanthogenate with Bu 3 SnH·Et 3 B, [31] and subsequent deprotection with DDQ [32] provided primary alcohol 25 in 78 % yield over three steps.…”
Section: Scheme 2 Retrosynthesis Of Gephyronic Acid (3)mentioning
confidence: 96%
“…The syn stereochemistry in 20 was supported by NMR analysis of lactone 22 derived from 20 (Scheme 4). [26] As the key step for coupling of the fragments 4 and 5, a stereodifferentiating BF 3 ·OEt 2 promoted Mukaiyama aldol reaction [27] was chosen (Scheme 5). Based on the facial selectivities of anti aldehyde 4 and the enolsilane of 5 we expected an anti-selective aldol formation.…”
Section: Scheme 2 Retrosynthesis Of Gephyronic Acid (3)mentioning
confidence: 99%
“…[30] In addition, various Lewis acid-catalyzed additions of silyl nucleophiles towards β-silyloxy aldehydes have been shown to proceed with remarkably high 1,3-anti-diastereoselectivities. [31][32][33] Based upon this precedence we investigated a number of Lewis acids (e.g. MeAlCl 2 , TiCl 4 , SnCl 4 , MgBr 2 ·OEt 2 ) as mediators for the reaction of silyl enol ether 19 and aldehyde 5 and eventually found BF 3 ·OEt 2 optimal.…”
Section: Doubly Diastereoselective Mukaiyama Aldol Reactionmentioning
confidence: 99%
“…[24] Durch NMR-Analyse des aus 20 erhaltenen Lactons 22 ließ sich die syn-Stereochemie in 20 belegen (Schema 4). [26] Als Schlüsselschritt zur Kupplung von 4 und 5 wählten wir eine stereodifferenzierende BF 3 ·OEt 2 -vermittelte Mukaiyama-Aldolreaktion, [27] in der wir aufgrund der facialen Selektivitäten des anti-Aldehyds 4 und des Enolsilans von 5 eine anti-selektive Aldolbildung [22a, 28, 29] erwarteten (Schema 5). In der Tat kuppelten das aus 5 erhaltene Enolsilan 23 und das Fragment 4 hauptsächlich zum Felkin-Diastereomer 24, dessen anti-Konfiguration an C8-C9 ein Vergleich der Kopplungskonstanten (J 8-H,9-H = 9.8, J 9-H,10-H = 1.4 Hz) mit denen strukturverwandter Verbindungen [27] eindeutig belegte.…”
unclassified
“…[26] Als Schlüsselschritt zur Kupplung von 4 und 5 wählten wir eine stereodifferenzierende BF 3 ·OEt 2 -vermittelte Mukaiyama-Aldolreaktion, [27] in der wir aufgrund der facialen Selektivitäten des anti-Aldehyds 4 und des Enolsilans von 5 eine anti-selektive Aldolbildung [22a, 28, 29] erwarteten (Schema 5). In der Tat kuppelten das aus 5 erhaltene Enolsilan 23 und das Fragment 4 hauptsächlich zum Felkin-Diastereomer 24, dessen anti-Konfiguration an C8-C9 ein Vergleich der Kopplungskonstanten (J 8-H,9-H = 9.8, J 9-H,10-H = 1.4 Hz) mit denen strukturverwandter Verbindungen [27] eindeutig belegte. Milde Desoxygenierung, d. h. Behandeln mit NaHMDS in CS 2 und MeI [30] und Reduktion des intermediären Xanthogenats mit Bu 3 SnH·Et 3 B, [31] und anschließendes Entschützen mit DDQ [32] lieferten den primären Alkohol 25 in 78 % Ausbeute über drei Stufen.…”
unclassified