Mild Procedure for the Catalytic Bis(stannylation) of Alkynes with Hexaalkylditins

Mancuso, John; Lautens, Mark

doi:10.1021/ol034284e

Cited by 39 publications

(17 citation statements)

References 24 publications

(14 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1,15,16 The successful sequence commenced with a palladium-catalyzed vic-distannation of a propargylic alcohol E to afford a synthon of type D (Scheme 2). 17,18 Upon proper choice of the catalyst and the reaction conditions, only the less-hindered terminal C−Sn moiety of D engages in a Stille reaction with a (Z)-configured alkenyl halide partner C; such site-selective cross coupling of 1,2-bistannylalkenes had been essentially unknown before. 19−21 The resulting product B lends itself to chlorodemetalation with retention of configuration to give the desired chlorodiene product A.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…We conjectured that our first-generation synthesis of nominal chagosensine methyl ester 2aa actually meets this strategic precondition well: Specifically, we had devised a new entry into the idiosyncratic chloro-1,3-diene unit of the target, after a number of other options had been ruled out. ,, The successful sequence commenced with a palladium-catalyzed vic -distannation of a propargylic alcohol E to afford a synthon of type D (Scheme ). , Upon proper choice of the catalyst and the reaction conditions, only the less-hindered terminal C–Sn moiety of D engages in a Stille reaction with a ( Z )-configured alkenyl halide partner C ; such site-selective cross coupling of 1,2-bistannylalkenes had been essentially unknown before. − The resulting product B lends itself to chloro-demetalation with retention of configuration to give the desired chlorodiene product A . − This sequence is inherently modular and hence deemed adequate for the preparation of the envisaged chagosensine “library” in a serial manner from the fragments 6 and 7 (Figure ).…”

Section: Resultsmentioning

confidence: 99%

“…Oxidation of the primary alcohol in 18 to the corresponding aldehyde was performed under modified Parikh-Doering conditions, in which the commonly used Et 3 N was replaced by ( i Pr) 2 NEt to prevent epimerization from occurring. The crude aldehyde proved very sensitive and was therefore directly used in the subsequent asymmetric alkynylation with trimethylsilylacetylene, which proceeded well on gram scale provided that all components had been scrupulously dried prior to use. , Selective cleavage of the C-silyl group of 19 with K 2 CO 3 in MeOH followed by palladium-catalyzed bis-stannylation of the released terminal alkyne completed the synthesis of the northern fragment 6a in the format corresponding to the originally assigned structure of chagosensine.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Chagosensine: A Riddle Wrapped in a Mystery Inside an Enigma

et al. 2020

View full text Add to dashboard Cite

The marine macrolide chagosensine is supposedly distinguished by a (Z,Z)-configured 1,3-chlorodiene contained within a highly strained 16-membered lactone ring, which also incorporates two trans-2,5-disubstituted tetrahydrofuran (THF) rings; this array is unique. After our initial synthesis campaign had shown that the originally proposed structure is incorrect, the published data set was critically revisited to identify potential mis-assignments. The “northern” THF ring and the anti-configured diol in the “southern” sector both seemed to be sites of concern, thus making it plausible that a panel of eight diastereomeric chagosensine-like compounds would allow the puzzle to be solved. To meet the challenge, the preparation of the required building blocks was optimized, and a convergent strategy for their assembly was developed. A key role was played by the cobalt-catalyzed oxidative cyclization of alken-5-ol derivatives (“Mukaiyama cyclization”), which is shown to be exquisitely chemoselective for terminal alkenes, leaving even terminal alkynes (and other sites of unsaturation) untouched. Likewise, a palladium-catalyzed alkyne alkoxycarbonylation reaction with formation of an α-methylene-γ-lactone proved instrumental, which had not found application in natural product synthesis before. Further enabling steps were a nickel-catalyzed “Tamaru-type” homocrotylation, stereodivergent aldehyde homologations, radical hydroindation, and palladium-catalyzed alkyne-1,2-bis-stannation. The different building blocks were assembled in a serial fashion to give the idiosyncratic chlorodienes by an unprecedented site-selective Stille coupling followed by copper-mediated tin/chlorine exchange. The macrolactones were closed under forcing Yamaguchi conditions, and the resulting products were elaborated into the targeted compound library. Yet, only one of the eight diastereomers turned out to be stable in the solvent mixture that had been used to analyze the natural product; all other isomers were prone to ring opening and/or ring expansion. In addition to this stability issue, our self-consistent data set suggests that chagosensine has almost certainly little to do with the structure originally proposed by the isolation team.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Chagosensine: A Riddle Wrapped in a Mystery Inside an Enigma

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Oxidative addition of hexaalkylditin [RЈ 3 Sn-SnRЈ 3 ] at palladium complexes in formal oxidation state zero Pd 0 or substitution at the dichloride [(RNC) 2 PdCl 2 ] are the discussed reaction pathways for the formation of the possible intermediate. [5][6][7] So far complexes of the discussed intermediate type have not been characterized by single-crystal structure solution. However complexes with the trichlorostannate ligand [SnCl 3 ] -like [(CNR) 2 Pd(SnCl 3 ) 2 ] (R = Ph, Cy) were characterized by elemental analysis and IR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Palladium Chemistry with Stanna‐closo‐dodecaborate and Isocyanides

Hornung

Wesemann

2010

Eur J Inorg Chem

View full text Add to dashboard Cite

The substitution equilibrium between isocyanides and stanna‐closo‐dodecaborate with palladium(II) was investigated. The mixed substituted products of type [(RNC)2Pd(SnB11H11)2]2– and [(RNC)Pd(SnB11H11)3]4– were characterized by X‐ray crystal structure analysis, elemental analysis and NMR spectroscopy. Isocyanide insertion into palladium–carbon bonds was also found. The zwitterionic complexes isolated from the reaction of [(P′2)Pd(Me)(SnB11H11)]– (P′2 = dppe, dppp, dppf) with isocyanides were characterized.

show abstract

“…The molybdenum complex showed comparable or even better selectivity than the palladium complex [PdCl 2 (PPh 3 ) 2 ] in the case of certain sterically hindered alkynes [6]. Another molybdenum complex, [Mo(CO) 3 (CN-t-Bu) 3 ], was found to be a catalyst for the hydrostannation reaction by Kazmaier et al [7e10]. In the presence of this catalyst, the hydrostannation of propargylic alcohols, ethers, amines, and amides gave rise to functionalized vinylstannanes in good yield.…”

Section: Introductionmentioning

confidence: 99%