1,722,395 research outputs found
MICHAEL MICHAEL MICHAEL
No full textFaculty adviser: Will DaddarioThis research was supported by the Undergraduate Research Opportunities Program (UROP).Broderick, Chase. (2013). MICHAEL MICHAEL MICHAEL. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/155448
Organocatalytic Oxa-Michael/Michael/Michael/Aldol Condensation Quadruple Domino Sequence: Asymmetric Synthesis of Tricyclic Chromanes
No full textAn efficient and highly stereoselective one-pot, four-component synthesis of functionalized tricyclic chromanes has been achieved through an organocatalyzed quadruple domino reaction. The reaction sequence involves an oxa-Michael/Michael/Michael/aldol condensation between alcohols, 2 equiv of acrolein, and nitrochromenes to generate the pharmaceutically important tricyclic chromanes bearing three contiguous stereogenic centers including a chiral tetrasubstituted carbon center in good domino yields (30–70%) and excellent diastereo- and enantioselectivities (>20:1 dr and >99% ee).peerReviewe
Stereoselective Synthesis of Chiral Hydrophenanthridines via a One-Pot Stepwise Aza-Michael/Michael/Michael Process
No full textA one-pot, two-step aza-Michael/Michael/Michael
process was developed
to diastereospecifically construct C6a,C10a-cis-hydrophenanthridines
in a highly enantioselective manner (83–99% ee). The tricyclic
products were provided in 50–99% isolated yields, sequentially
promoted by bifunctional squaramide and diamine in a one-pot operation.
This doubly annulative protocol indicated that the complicated polycyclic
structures could be easily constructed via full employment of the
available reaction sites of readily prepared precursors
Study of Michael-Michael-retro Michael addition catalyzed, by 9-amino-9-deoxyepiquinine using ESI-MS
No full textThe Michael-Michael-retro Michael addition catalyzed by 9-amino-9-deoxyepiquinine was monitored and the major intermediates and catalyst in the catalytic cycle were detected and characterized using ESI-MS/MS for the first time. Some important isomeric intermediates including isomeric enamine and imine structures were tentatively differentiated and further studied by theoretical calculations. Fragment ions of protonated catalyst indicate that proton possibly influences the conformation of the catalyst
A General Organocatalyzed Michael–Michael Cascade Reaction Generates Functionalized Cyclohexenes
No full textAlthough β-dicarbonyl compounds are regularly employed as Michael donors, intermediates arising from the Michael addition of unsaturated β-ketoesters to α,β-unsaturated aldehydes are susceptible to multiple subsequent reaction pathways. We designed cyclic unsaturated β-ketoester substrates that enabled the development of the first diphenyl prolinol silyl ether catalyzed Michael–Michael cascade reaction initiated by a β-dicarbonyl Michael donor to form cyclohexene products. The reaction conditions we developed for this Michael–Michael cascade reaction were also amenable to a variety of linear unsaturated β-ketoester substrates, including some of the same linear unsaturated β-ketoester substrates that were previously ineffective in Michael–Michael cascade reactions. These studies thus revealed that a change in simple reaction conditions, such as solvent and additives, enables the same substrate to undergo different cascade reactions, thereby accessing different molecular scaffolds. These studies also culminated in the development of a general organocatalyzed Michael–Michael cascade reaction that generates highly functionalized cyclohexenes with up to four stereocenters, in up to 97% yield, 32:1 dr, and 99% ee, in a single step from a variety of unsaturated β-ketoesters
A General Organocatalyzed Michael–Michael Cascade Reaction Generates Functionalized Cyclohexenes
No full textAlthough β-dicarbonyl compounds are regularly employed as Michael donors, intermediates arising from the Michael addition of unsaturated β-ketoesters to α,β-unsaturated aldehydes are susceptible to multiple subsequent reaction pathways. We designed cyclic unsaturated β-ketoester substrates that enabled the development of the first diphenyl prolinol silyl ether catalyzed Michael–Michael cascade reaction initiated by a β-dicarbonyl Michael donor to form cyclohexene products. The reaction conditions we developed for this Michael–Michael cascade reaction were also amenable to a variety of linear unsaturated β-ketoester substrates, including some of the same linear unsaturated β-ketoester substrates that were previously ineffective in Michael–Michael cascade reactions. These studies thus revealed that a change in simple reaction conditions, such as solvent and additives, enables the same substrate to undergo different cascade reactions, thereby accessing different molecular scaffolds. These studies also culminated in the development of a general organocatalyzed Michael–Michael cascade reaction that generates highly functionalized cyclohexenes with up to four stereocenters, in up to 97% yield, 32:1 dr, and 99% ee, in a single step from a variety of unsaturated β-ketoesters
Organocatalytic Enantioselective Michael–Michael–Michael–Aldol Condensation Reactions: Control of Five Stereocenters in a Quadruple-Cascade Asymmetric Synthesis of Highly Functionalized Hexahydrophenanthrenes
No full textA cascade
organocatalysis has been developed for the enantioselective
synthesis of a highly functionalized hexahydrophenanthrene-2-carbaldehyde
containing five contiguous stereogenic centers with high diastereoselectivity
and high enantioselectivity (>99% ee). The one-pot
method comprises a cascade of organocatalytic Michael–Michael–Michael–aldol
reactions of 2-methyl-1,5-dinitro-3-((E)-2-nitrovinyl)benzene
and α,β-unsaturated aldehydes (e.g., cinnamaldehyde).
The structure and absolute configuration of a product were confirmed
by X-ray analysis of an appropriate derivative
A New Organocatalyzed Michael−Michael Cascade Reaction Generates Highly Substituted Fused Carbocycles
No full textWhile β-ketoesters are useful Michael donors, they were previously ineffective in Michael−Michael cascade reactions using α,β-unsaturated aldehydes in conjunction with diphenylprolinol silyl ether organocatalysts. However, through rational modification of substrates and manipulation of the catalytic cycle, we developed an efficient Michael−Michael cascade reaction using β-ketoesters of type 9. In this transformation, highly substituted fused carbocycles are generated in a single step in up to 87% yield and 99% ee
A New Organocatalyzed Michael−Michael Cascade Reaction Generates Highly Substituted Fused Carbocycles
No full textWhile β-ketoesters are useful Michael donors, they were previously ineffective in Michael−Michael cascade reactions using α,β-unsaturated aldehydes in conjunction with diphenylprolinol silyl ether organocatalysts. However, through rational modification of substrates and manipulation of the catalytic cycle, we developed an efficient Michael−Michael cascade reaction using β-ketoesters of type 9. In this transformation, highly substituted fused carbocycles are generated in a single step in up to 87% yield and 99% ee
Organocatalyzed Michael–Michael Cascade Reaction: Asymmetric Synthesis of Polysubstituted Chromans
No full textAn
enantioselective cascade Michael–Michael reaction between
chalcones enolates and nitromethane catalyzed by a bifunctional thiourea
is developed. This reaction provides a mild but efficient approach
to chiral benzopyrans bearing three consecutive stereocenters in high
yields with excellent stereoselectivities, and the benzopyrans can
be easily transformed to the corresponding tricyclic product
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