Tandem transformations initiated and determined by the Michael reaction

Gorobets, E. V.; Мифтахов, М. С.; Валеев, Ф. А.

doi:10.1070/rc2000v069n12abeh000614

Cited by 42 publications

(7 citation statements)

References 86 publications

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“…11,17 In this paper, we have shown that the unexpected domino sequence of these reactions starting from alkylthioacetic aldehydes as CH-acids, diethylamine and dihalomethane leads to 2,4-dialkylthio pentanedials. The dehydroamination of the intermediate β-diethylamine aldehyde is a middle stage of this process.…”

Section: Discussionmentioning

confidence: 99%

Unexpected one-flask synthesis of 2,4-dialkylthiopentanedials via the reaction of alkylthioacetic aldehydes with dihalomethane and diethylamine

Keiko¹,

Stepanova²,

Verochkina³

et al. 2009

Arkivoc

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The reaction of alkylthioacetic aldehydes with dihalomethane and diethylamine has allowed the unexpected domino sequence of three reactions (Mannich − dehydroamination − Michael) to be revealed. A facile one-pot three-step protocol for the synthesis of 2,4-dialkylthio pentanedials in up to 65 % yield has been developed on the basis of this reaction. A biological activity of one pentadial has been determined for the first time. The activity of alkylthioacetic aldehydes as a CH-acids is shown in two anion reactions.

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Section: Discussionmentioning

confidence: 99%

Unexpected one-flask synthesis of 2,4-dialkylthiopentanedials via the reaction of alkylthioacetic aldehydes with dihalomethane and diethylamine

Keiko¹,

Stepanova²,

Verochkina³

et al. 2009

Arkivoc

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“…Herein we report that Cp*Co III ‐catalysts not only facilitate three‐component additions to a wide array of aldehydes, including electron poor and rich aromatic, alkenyl, and branched and unbranched alkyl derivatives, but that the transformation also proceeds with high diastereoselectivities ranging from 87:13 to >98:2 d.r. (Figure c) . Moreover, we disclose the first asymmetric C−H bond functionalization reaction employing Cp*Co III catalysts, with three‐component C−H bond addition cascades to N‐tert ‐butanesulfinyl imines (Figure d).…”

Section: Figurementioning

confidence: 99%

Highly Stereoselective Cobalt(III)‐Catalyzed Three‐Component C−H Bond Addition Cascade

2016

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A highly stereoselective three-component C(sp 2 )ÀH bond addition across alkene and polarized p-bonds is reported for which Co III catalysis was shown to be much more effective than Rh III . The reaction proceeds at ambient temperature with both aryl and alkyl enones employed as efficient coupling partners. Moreover, the reaction exhibits extremely broad scope with respect to the aldehyde input; electron rich and poor aromatic, alkenyl, and branched and unbranched alkyl aldehydes all couple in good yield and with high diastereoselectivity. Multiple directing groups participate in this transformation, including pyrazole, pyridine, and imine functional groups. Both aromatic and alkenyl C(sp 2 ) À H bonds undergo the three-component addition cascade, and the alkenyl addition product can readily be converted into diastereomerically pure five-membered lactones. Additionally, the first asymmetric reactions with Co III -catalyzed CÀH functionalization are demonstrated with three-component C À H bond addition cascades employing N-tert-butanesulfinyl imines. These examples represent the first transition metal catalyzed CÀH bond additions to N-tert-butanesulfinyl imines, which are versatile and extensively used intermediates for the asymmetric synthesis of amines.C À H functionalization has emerged as a core strategy to access synthetically useful structural motifs, many of which are found in drugs and natural products. [1,2] Of the many transition-metal catalysts that facilitate this process, Rh III catalysts have been demonstrated to be among the most useful because of their unique reactivity and high functional group compatibility.[3] Following the seminal reports of Co III -catalyzed C À H functionalization [4] by Kanai and Matsunaga in 2013, [5ac] a number of groups (including our own) have demonstrated that earth abundant Co III catalysts can provide analogous reactivity to their second row Rh III congeners. [4,5] For some transformations divergent reactivity is displayed between Cp*Co III and Cp*Rh III catalysts, [6] but significant differences in non-annulative redox-neutral couplings have yet to be reported. Recently, we described preliminary results on a three-component CÀH functionalization cascade by Rh III -catalysis (Figure 1 a). [7] Though the transformation proceeded in good yield, very poor diastereoselectivity was observed. After thorough investigation, only ethyl glyoxylate was reactive in the three-component transformation (Figure 1 a,b). Herein we report that Cp*Co III -catalysts not only facilitate three-component additions to a wide array of aldehydes, including electron poor and rich aromatic, alkenyl, and branched and unbranched alkyl derivatives, but that the transformation also proceeds with high diastereoselectivities ranging from 87:13 to > 98:2 d.r. (Figure 1 c). [8,9] Moreover, we disclose the first asymmetric C À H bond functionalization reaction employing Cp*Co III catalysts, with three-component CÀH bond addition cascades to N-tert-butanesulfinyl imines (Figure 1 d).Our initi...

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“…In terms of their selectivities and yields, both aza-Michael 3c, 7 and olefin metathesis reactions 8 exhibit suitable properties for participation in effective tandem protocols. In fact, each of these reactions has been combined with other types of transformations in many tandem sequences.…”

Section: Scheme 1 Intramolecular Aza-michael Reactionsmentioning

confidence: 99%

A New Tandem Cross Metathesis-Intramolecular Aza-Michael Reaction for the Synthesis of α,α-Difluorinated Lactams

Fustero¹,

Báez²,

Sánchez‐Roselló³

et al. 2012

Synthesis

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A new tandem cross metathesis-intramolecular azaMichael reaction in which an α,α-difluorinated amide serves as a source of nucleophilic nitrogen is described. This process gives rise to a new family of fluorinated γ-and δ-lactams. The tandem protocol is catalyzed by the Hoveyda-Grubbs second-generation ruthenium catalyst with titanium(IV) tetraisopropoxide as a co-catalyst and it is highly efficient when conjugated ketones are used as the Michael acceptors. With conjugated esters, however, it is necessary to perform a step-by-step procedure in which the cyclization event is activated by the addition of a base. An asymmetric version of the process is also evaluated.Tandem processes usually generate high levels of molecular complexity in a single chemical operation thereby minimizing the use of solvents and reagents and reducing the time and number of steps involved in purification. These advantages make tandem transformations extremely appealing from both academic and industrial points of view. Indeed, tandem protocols have been extensively developed in recent decades, and they have found a wide variety of applications in natural-product synthesis. 1 Moreover, asymmetric versions greatly enhance the usefulness and relevance of tandem reactions and these have become extremely powerful and popular tools for synthetic organic chemists. 2The conjugated addition of nitrogen-centered nucleophiles to the β-carbon of electron-deficient olefins, the socalled aza-Michael reaction (AMR), is a particularly interesting transformation because it probably represents the shortest route to β-amino carbonyl derivatives, such as β-amino acids. Furthermore, a wide variety of nitrogen nucleophiles and Michael acceptors can participate in this process, which is also simple and displays significant atom economy. 3 The intramolecular version of the AMR is especially relevant because it permits the direct generation of nitrogen-containing heterocycles, yielding natural products and pharmaceutically relevant molecules in a relatively simple manner (Scheme 1). 4Olefin metathesis is one of the most powerful methods for the formation of carbon-carbon double bonds. 5 In comparison with the ring-closing metathesis reaction, the cross metathesis (CM) variant was initially underdeveloped because of a lack of predictability in the product distribution and the stereoselectivity of the reaction. However, the development of new ruthenium-based complexes that exhibit improved efficiency and tolerance to various functional groups changed the situation and it is now possible to achieve perfect control of E/Z selectivity in CM reactions. 6 Scheme 1 Intramolecular aza-Michael reactionsIn terms of their selectivities and yields, both azaMichael 3c,7 and olefin metathesis reactions 8 exhibit suitable properties for participation in effective tandem protocols. In fact, each of these reactions has been combined with other types of transformations in many tandem sequences. However, only a few examples of combinations of CM and AMR have been reported, probably...

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Tandem transformations initiated and determined by the Michael reaction

Cited by 42 publications

References 86 publications

Unexpected one-flask synthesis of 2,4-dialkylthiopentanedials via the reaction of alkylthioacetic aldehydes with dihalomethane and diethylamine

Unexpected one-flask synthesis of 2,4-dialkylthiopentanedials via the reaction of alkylthioacetic aldehydes with dihalomethane and diethylamine

Highly Stereoselective Cobalt(III)‐Catalyzed Three‐Component C−H Bond Addition Cascade

A New Tandem Cross Metathesis-Intramolecular Aza-Michael Reaction for the Synthesis of α,α-Difluorinated Lactams

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