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Atom-efficient gold(I)-chloride-catalyzed synthesis of α-sulfenylated carbonyl compounds from propargylic alcohols and aryl thiols: substrate scope and experimental and theoretical mechanistic investigation.

Biswas S, Dahlstrand C, Watile RA, Kalek M, Himo F, Samec JS - Chemistry (2013)

Bottom Line: A sulfenylated allylic alcohol, generated by initial regioselective attack of the aryl thiol on the triple bond of the propargylic alcohol, was isolated, evaluated, and found to be an intermediate in the reaction.Density functional theory (DFT) calculations showed that the observed regioselectivity of the aryl thiol attack towards the 2-position of propargylic alcohol was determined by a low-energy, five-membered cyclic protodeauration transition state instead of the strained, four-membered cyclic transition state found for attack at the 3-position.This in turn allows for a 1,2-hydride shift, generating the final product of the reaction.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, BMC, Uppsala University, Box 576, 75123, Uppsala (Sweden), Fax: (+46) 018-471-3818.

No MeSH data available.


Optimized transition-state structures for the key steps of the gold-catalyzed isomerization of allylic alcohol 5 to aldehyde 3 i.
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fig04: Optimized transition-state structures for the key steps of the gold-catalyzed isomerization of allylic alcohol 5 to aldehyde 3 i.

Mentions: The catalytic cycle for the rearrangement of 5Z into 3 i starts with complex INT4(Z). Under the normal reaction conditions thiophenol 2 a is present in the reaction mixture in excess and may act as a proton donor. Thus, in the first step of the reaction, 2 a, acidified by coordination of AuCl to the sulfur atom, protonates the double bond of allylic alcohol 5Z at the 3-position (TS4(Z), see Figure 4 for the optimized structure). The calculated barrier is 16.4 kcal mol−1 relative to INT4(Z), and the resulting dissociated ion-pair intermediate INT5 lies 7.0 kcal mol−1 higher than INT4(Z) (see Figure 3 for the free-energy diagram). Since the transition state for the following step of the catalytic cycle (TS5) is higher in energy than TS4(Z), the protonation is reversible.


Atom-efficient gold(I)-chloride-catalyzed synthesis of α-sulfenylated carbonyl compounds from propargylic alcohols and aryl thiols: substrate scope and experimental and theoretical mechanistic investigation.

Biswas S, Dahlstrand C, Watile RA, Kalek M, Himo F, Samec JS - Chemistry (2013)

Optimized transition-state structures for the key steps of the gold-catalyzed isomerization of allylic alcohol 5 to aldehyde 3 i.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4524420&req=5

fig04: Optimized transition-state structures for the key steps of the gold-catalyzed isomerization of allylic alcohol 5 to aldehyde 3 i.
Mentions: The catalytic cycle for the rearrangement of 5Z into 3 i starts with complex INT4(Z). Under the normal reaction conditions thiophenol 2 a is present in the reaction mixture in excess and may act as a proton donor. Thus, in the first step of the reaction, 2 a, acidified by coordination of AuCl to the sulfur atom, protonates the double bond of allylic alcohol 5Z at the 3-position (TS4(Z), see Figure 4 for the optimized structure). The calculated barrier is 16.4 kcal mol−1 relative to INT4(Z), and the resulting dissociated ion-pair intermediate INT5 lies 7.0 kcal mol−1 higher than INT4(Z) (see Figure 3 for the free-energy diagram). Since the transition state for the following step of the catalytic cycle (TS5) is higher in energy than TS4(Z), the protonation is reversible.

Bottom Line: A sulfenylated allylic alcohol, generated by initial regioselective attack of the aryl thiol on the triple bond of the propargylic alcohol, was isolated, evaluated, and found to be an intermediate in the reaction.Density functional theory (DFT) calculations showed that the observed regioselectivity of the aryl thiol attack towards the 2-position of propargylic alcohol was determined by a low-energy, five-membered cyclic protodeauration transition state instead of the strained, four-membered cyclic transition state found for attack at the 3-position.This in turn allows for a 1,2-hydride shift, generating the final product of the reaction.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, BMC, Uppsala University, Box 576, 75123, Uppsala (Sweden), Fax: (+46) 018-471-3818.

No MeSH data available.