“…This study extended the synthetic utility of acylsilanes . Although there are many methods for the preparation of silyl enol ethers, most of them employ strongly basic conditions . Our radical approach works under neutral conditions and may offer some advantages when base-sensitive functionalities are present.…”
Section: Discussionmentioning
confidence: 92%
“…Although the use of a bulky base may give the regioisomer such as 30 , the other isomer cannot be eliminated completely. Our method provides a useful approach in addition to other methods. , …”
Section: Resultsmentioning
confidence: 99%
“…We found that this route can be realized by the use of phenylsulfonyl group . In this paper, we describe our full investigation of the use of these two approaches in the regiospecific formation of silyl enol ethers. , 1 …”
Section: Introductionmentioning
confidence: 99%
“…Silyl enol ethers are important synthetic intermediates. There are two widely used methodologies for their synthesis . One is to generate silyl enol ethers from ketones and aldehydes.…”
Section: Introductionmentioning
confidence: 99%
“…Both methodologies are performed under basic conditions. Alternatively, silyl enol ethers can be prepared from acylsilanes. , In this regard, a useful method involves the coupling of an acylsilane with a carbanion bearing α-leaving group (eq 1) was developed by Reich et al The initial adduct undergoes a Brook rearrangement, and the resulting silyloxy substituted carbanion fragments to give the silyl enol ether regiospecifically. The leaving group can also be placed at the α-position of the acylsilane as shown in eq 2 .…”
Acylsilanes with terminal alpha-stannyl bromide or xanthate functionalities are prepared. Alpha-stannyl radicals generated from these acylsilanes undergo intramolecular cyclizations to give cyclic silyl enol ethers regiospecifically. The radical processes involve radical cyclization, Brook rearrangement, and beta-fragmentation in sequence. A tributylstannyl group serves as the radical leaving group. The newly formed sigma-bond and pi-bond are located between the same two carbon atoms. This approach is limited to the formation of five-membered rings. In another route, omega-bromo-alpha-phenylsulfonylacylsilanes are synthesized. The radical cyclizations of these alpha-sulfonylacylsilanes also give cyclic silyl enol ethers. The phenylsulfonyl moiety is the radical leaving group in this system. Furthermore, the newly formed sigma-bond and pi-bond are located at adjacent positions sharing a single carbon atom. The latter approach is effective for both five- and six-membered ring formation.
“…This study extended the synthetic utility of acylsilanes . Although there are many methods for the preparation of silyl enol ethers, most of them employ strongly basic conditions . Our radical approach works under neutral conditions and may offer some advantages when base-sensitive functionalities are present.…”
Section: Discussionmentioning
confidence: 92%
“…Although the use of a bulky base may give the regioisomer such as 30 , the other isomer cannot be eliminated completely. Our method provides a useful approach in addition to other methods. , …”
Section: Resultsmentioning
confidence: 99%
“…We found that this route can be realized by the use of phenylsulfonyl group . In this paper, we describe our full investigation of the use of these two approaches in the regiospecific formation of silyl enol ethers. , 1 …”
Section: Introductionmentioning
confidence: 99%
“…Silyl enol ethers are important synthetic intermediates. There are two widely used methodologies for their synthesis . One is to generate silyl enol ethers from ketones and aldehydes.…”
Section: Introductionmentioning
confidence: 99%
“…Both methodologies are performed under basic conditions. Alternatively, silyl enol ethers can be prepared from acylsilanes. , In this regard, a useful method involves the coupling of an acylsilane with a carbanion bearing α-leaving group (eq 1) was developed by Reich et al The initial adduct undergoes a Brook rearrangement, and the resulting silyloxy substituted carbanion fragments to give the silyl enol ether regiospecifically. The leaving group can also be placed at the α-position of the acylsilane as shown in eq 2 .…”
Acylsilanes with terminal alpha-stannyl bromide or xanthate functionalities are prepared. Alpha-stannyl radicals generated from these acylsilanes undergo intramolecular cyclizations to give cyclic silyl enol ethers regiospecifically. The radical processes involve radical cyclization, Brook rearrangement, and beta-fragmentation in sequence. A tributylstannyl group serves as the radical leaving group. The newly formed sigma-bond and pi-bond are located between the same two carbon atoms. This approach is limited to the formation of five-membered rings. In another route, omega-bromo-alpha-phenylsulfonylacylsilanes are synthesized. The radical cyclizations of these alpha-sulfonylacylsilanes also give cyclic silyl enol ethers. The phenylsulfonyl moiety is the radical leaving group in this system. Furthermore, the newly formed sigma-bond and pi-bond are located at adjacent positions sharing a single carbon atom. The latter approach is effective for both five- and six-membered ring formation.
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