Stereoselective Synthesis of Tetrahydropyrans via a Formal [4 + 2]-Cycloaddition of Allylsilanes

and, Steven R. Angle; El-Said, Nahla A.

doi:10.1021/ja991861e

Cited by 31 publications

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References 17 publications

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“…Although these catalysts were reported to be catalytically active for the addition of allylsilanes to aldehydes and imines, [4] our results reveal that AgOTf, [PPh 3 AuSbF 6 ], and [PPh 3 AuOTf] are less efficient than platinum catalysts. [8] Treatment of 2-alkynylbenzaldehyde 1 a with PtCl 2 (5 mol %) in hot toluene (Table 1, entry 1) gave oxatricyclic species 3 a and siloxy species 2 a in 32 % and 39 % yields, respectively.…”

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confidence: 74%

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confidence: 99%

“…[2] New [3+2] and [4+2] annulations were reported for aldehyde substrates bearing an a-or b-siloxy group, [3] but these annulations required 1.0-5.0 equivalents of a Lewis acid (BF 3 ·Et 2 O, TiCl 4 , or SnCl 4 ). [2][3][4] Our objective was to explore new annulations of allysilanes with functionalized aldehydes by using soft-acid-metal species in catalytic proportions. [4,5] Herein, we report a one-pot Pt II -catalyzed synthesis of 9-oxabicyclo[3.3.1]nona-2,6-dienes by a tandem allylation/annulation reaction of the oxo-alkyne functionalities with 2-substituted allylsilanes (see Table 1).…”

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Pt^II‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade

2008

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Pt^II‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade

2008

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“…111,112 On the other hand, allylgallation of alkynes proceeds when the reaction is carried out by using a stoichiometric amount of GaCl 3 (eq 34 Stereoselective Allylation Reaction. 134 On the other hand, tetrahydroquinolines can be prepared from the SnCl 4mediated reaction of N-aryl-1H-benzotriazoyl-1-methanamines with allyltrimethylsilane. One example is the use of a chiral acyloxy borane (CAB) catalyst.…”

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confidence: 99%

Allyltrimethylsilane

Fleming

Asao

2006

Encyclopedia of Reagents for Organic Synthesis

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“…6). Use of an additive, namely 2,6-di-tert-butyl-4-methylpyridine, [13] to remove traces of acid that would cause unwanted protodesilylation was ineffective. However, formation of 14 could be prevented by use of BF 3 ·OEt 2 freshly distilled over calcium hydride to give only 13 in 50 % yield.…”

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Bimetallic Reagents of Silicon: One‐Pot Synthesis of 2,3,5‐Trisubstituted Tetrahydrofurans by a Double Sakurai–Hosomi Reaction

2004

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Unsaturated bimetallic reagents containing Group 14 metals, such as silicon and tin, have recently emerged as versatile coupling reagents in organic synthesis. [1, 2] These reagents are particularly appealing when both metals employ a "ferryman" service to yield metal-free cyclic products in a one-pot reaction. However, examples of such reactions are rare. [2] As part of our interest in allyl organometallic compounds of silicon, [3] we envisioned that 1-silylmethyl allylic silanes 1 could be useful synthetic building blocks. In the presence of a Lewis acid, a bis-silyl reagent such as 1 affords a b-silyl carbocation 2 (Scheme 1) when treated with an aldehyde. This carbocation may then collapse to give an oxetane 3 (path a) [4] or, more likely, undergo a 1,2-silyl migration to give the thermodynamically favored bis-b-silyl carbocation 4, [5] which produces a trisubstituted tetrahydrofuran 5 (path b).[6] The latter was realized recently by Peng and Woerpel. [7] Additionally, a third pathway is also conceivable wherein 2 collapses to give a new allylic silane 6. The allylic silane 6 should be less reactive than the starting allylic silane 1 because its p bond is more hindered. Introduction of a second aldehyde should yield a silicon-free tetrahydrofuran 8 by trapping of the oxocarbenium ion 7 (path c). While our studies were in progress Smitrovich and Woerpel [8] reported a single experiment on the synthesis of a tetrahydrofuran lacking silyl groups by reaction of a substituted silylmethyl allylic silane and an aldehyde; however, a pure product could not be obtained and a furan structure was only tentatively assigned. Herein, we provide the first report that silylmethyl allylic silanes of type 1 can be channeled through path c to yield only 2,3,5-trisubstituted tetrahydrofurans.As the 1-silylmethyl allylic silanes 1 a,b (Scheme 2) selected for our study are novel, there were no reported procedures for their synthesis. Smitrovich and Woerpel experienced great difficulties in preparing similar compounds but eventually succeeded by employing allylic displacement, [9] which unfortunately could not be applied in our case since only carbamates from secondary allyl alcohols are amenable to it. Thus, a convenient synthetic methodology to this family of allylic silanes was our initial task. Our successful route (Scheme 2) involved heating disilanyl ether 9 (prepared in

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Stereoselective Synthesis of Tetrahydropyrans via a Formal [4 + 2]-Cycloaddition of Allylsilanes

Cited by 31 publications

References 17 publications

Pt^II‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade

Pt^II‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade

Allyltrimethylsilane

Bimetallic Reagents of Silicon: One‐Pot Synthesis of 2,3,5‐Trisubstituted Tetrahydrofurans by a Double Sakurai–Hosomi Reaction

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Stereoselective Synthesis of Tetrahydropyrans via a Formal [4 + 2]-Cycloaddition of Allylsilanes

Cited by 31 publications

References 17 publications

PtII‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade

PtII‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade

Allyltrimethylsilane

Bimetallic Reagents of Silicon: One‐Pot Synthesis of 2,3,5‐Trisubstituted Tetrahydrofurans by a Double Sakurai–Hosomi Reaction

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Pt^II‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade

Pt^II‐Catalyzed Synthesis of 9‐Oxabicyclo[3.3.1]nona‐2,6‐dienes from 2‐Alkynyl‐1‐carbonylbenzenes and Allylsilanes by an Allylation/Annulation Cascade