Controlled carbometalation. 20. Carbometalation reaction of alkynes with organoalene-zirconocene derivatives as a route to stereo-and regiodefined trisubstituted alkenes

Negishi, Ei‐ichi; Horn, David Van; Yoshida, Tadao

doi:10.1021/ja00309a036

Cited by 258 publications

(139 citation statements)

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“…[25] The PMB group was removed with DDQ (96 %), and then the alkynol intermediate was converted into vinyl iodide 12 using Negishis carbozirconation methodology (65 %). [26] The yield of 12 for this five step sequence was 54 % (attempts to perform the Negishi carbometalation sequence before the PMB group was removed were largely unsuccessful). The vinyl iodide 12 was elaborated to the allylic alcohol 13 in 89 % yield by a sequence of Moffatt ± Swern oxidation, [24] stabilized Wittig olefination, and DIBAL-H reduction.…”

Section: Receivedmentioning

confidence: 99%

Total Synthesis of (−)-Bafilomycin A1: Application of Diastereoselective Crotylboration and Methyl Ketone Aldol Reactions

Scheidt¹,

Tasaka²,

Bannister³

et al. 1999

Angew. Chem. Int. Ed.

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Section: Receivedmentioning

confidence: 99%

Total Synthesis of (−)-Bafilomycin A1: Application of Diastereoselective Crotylboration and Methyl Ketone Aldol Reactions

Scheidt¹,

Tasaka²,

Bannister³

et al. 1999

Angew. Chem. Int. Ed.

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“…In the case of terminal alkynes, the scandium was replaces by a zirconium catalyst, well-known for methylalumination [79]. For all products obtained, the CO 2 unit was introduced on the less hindered carbon.…”

Section: Scheme 2331: Hydrogenative and Methylative Carboxylation mentioning

confidence: 99%

Copper–NHC complexes in catalysis

Lazreg

Nahra

Cazin

2015

Coordination Chemistry Reviews

232

110

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“…A later report (30) on a closely related reaction with ''cationic'' chiral zirconocene derivatives should be noted. Clearly, from the results presented above, the Zr-catalyzed carbometallation is multimechanistic (23,(31)(32)(33)(34)(35)(36) and sensitive to several critical factors including ligands (22), solvents (23), and metal countercations of alkylmetals. With respect to metal countercations, the following generalizations may be presented as useful guidelines (36).…”

Section: Design Of Protocolsmentioning

confidence: 99%

An efficient and general route to reduced polypropionates via Zr-catalyzed asymmetric C—C bond formation

Negishi

Tan²,

Liang³

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

104

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An efficient and general method for the synthesis of reduced polypropionates has been developed through the application of asymmetric carboalumination of alkenes catalyzed by dichlorobis(1-neomenthylindenyl)zirconium [(NMI) 2ZrCl2]. In this investigation, attention has been focused on those reduced polypropionates that are ␣-monoheterofunctional and either -ethyl or -n-propyl. The reaction of 3-buten-1-ol with triethylaluminum (Et 3 Al) or tripropylaluminum ( n Pr3Al) in the presence of (NMI)2ZrCl2 and isobutylaluminoxane gave, after protonolysis, (R)-3-methyl-1-pentanol as well as (R)-and (S)-3-methyl-1-hexanols in 88 -92% yield in 90 -92% enantiomeric excess in one step. These 3-monomethyl-1-alkanols were then converted to two stereoisomers each of 2,4-dimethyl-1-hexanols and 2,4-dimethyl-1-heptanols via methylalumination catalyzed by (NMI) 2ZrCl2 and methylaluminoxane followed by oxidation with O 2. The four-step (or three-isolation-step) protocol provided syn-2,4-dimethyl-1-alkanols of >98% stereoisomeric purity in Ϸ50% overall yields, whereas (2S,4R)-2,4-dimethyl-1-hexanol of comparable purity was obtained in 40% overall yield. Commercial availability of (S)-2-methyl-1-butanol as a relatively inexpensive material suggested its use in the synthesis of (2S,4S)-and (2R,4S)-2,4-dimethyl-1-hexanols via a three-step protocol consisting of (i) iodination, (ii) zincation followed by Pd-catalyzed vinylation, and (iii) Zr-catalyzed methylalumination followed by oxidation with O 2. This three-step protocol is iterative and applicable to the synthesis of reduced polypropionates containing three or more branching methyl groups, rendering this method for the synthesis of reduced polypropionates generally applicable. Its synthetic utility has been demonstrated by preparing the side chain of zaragozic acid A and the C11-C20 fragment of antibiotics TMC-151 A-F. O ligo-and poly(alkene)s with methyl groups bonded to alternating carbon atoms in the main chain (compound 1 in Fig. 1) are important structural units in both polymer materials chemistry (1) and natural products chemistry. The latter includes those reduced polypropionates that contain (i) two methylbranched asymmetric carbon centers, such as zaragozic acid A (compound 2 in Fig. 1) (2), and (ii) three methyl-branched asymmetric carbon centers, such as antibiotics TMC-151 A-F (compound 3 in Fig. 1) (3). The degree of polymerization of poly(propylene) usually exceeds 10 3 . As a consequence, most of the methyl-branched carbon centers may be considered to be ''virtually achiral,'' rendering their absolute configuration practically insignificant. On the other hand, their relative stereochemistry, termed tacticity, is of crucial importance in various respects. In the cases of reduced polypropionates, where the degree of polymerization is mostly Ͻ10, typically 2-4, both absolute and relative configurations of compound 1 (Fig. 1) are critically important. It is therefore essential to construct each methyl-bearing asymmetric carbon center with the correct absolute configurati...

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Controlled carbometalation. 20. Carbometalation reaction of alkynes with organoalene-zirconocene derivatives as a route to stereo-and regiodefined trisubstituted alkenes

Cited by 258 publications

References 0 publications

Total Synthesis of (−)-Bafilomycin A1: Application of Diastereoselective Crotylboration and Methyl Ketone Aldol Reactions

Total Synthesis of (−)-Bafilomycin A1: Application of Diastereoselective Crotylboration and Methyl Ketone Aldol Reactions

Copper–NHC complexes in catalysis

An efficient and general route to reduced polypropionates via Zr-catalyzed asymmetric C—C bond formation

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