1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU): A Versatile Reagent in Organic Synthesis

Nand, Bhaskara; Khanna, Garima; Chaudhary, Ankita; Lumb, Anshika; Khurana, Jitender M.

doi:10.2174/1385272819666150402221133

“…1,8-Diazabicyclo [5.4.0]undec-7-ene (DBU) is a bicyclic and sterically hindered amidine possessing strong basic properties (pKa � 12 in water) [1][2][3] which has been used in a variety of organic reactions. [1,4,5] Although often regarded as a hindered and nonnucleophilic strong base, it nevertheless possesses nucleophilic properties [6] as exemplified with the DBU-catalyzed efficient Baylis-Hillman reaction (Scheme 1). [7] This reaction involves Michael-type addition of DBU to an α,β-ethylenic ketone leading to 1A.…”

Section: Introductionmentioning

confidence: 99%

DBU: A Reaction Product Component

Мuzart

¹

2020

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DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) is traditionally considered to be a non-nucleophilic base. Nevertheless, DBU possesses nucleophilic properties which mediate organic reactions and may lead to the formation of compounds containing the DBU scaffold. Participation of water to the processes affords there-component products. The review covers the reactions leading to DBU derivatives showing that the interest of this sterically hindered amidine is not limited to its basic role. Proposed mechanisms are described with, in some cases, personal comments.

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“…Amidines are useful substrates with a variety of applications. The amidine structure in 1,8-diazabicyclo [5.4.0]un-dec-7-ene (DBU) is used frequently as a non-nucleophilic base in synthetic chemistry, 1 and more complex amidines are even considered to be "superbases". 2 Amidines also have been used as ligands for organometallic complexes 3 and as starting material for the synthesis of N-heterocycles.…”

Section: Introductionmentioning

confidence: 99%

Efficient Copper Catalyzed Multi-component Synthesis of N-acyl amidines via Acyl Nitrenes

Vliet¹,

Polak²,

Siegler³

et al. 2019

Preprint

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Direct synthetic routes to amidines are desired, as they are widely present in many biologically active compounds and organometallic complexes. N-Acyl amidines in particular can be used as a starting material for the synthesis of heterocycles and have several other applications. Here, we describe a fast and practical copper catalyzed 3-component reaction of aryl acetylenes, amines and easily accessible 1,4,2-dioxazol-5-ones to N-acyl amidines, generating CO2 as the only by-product. Transformation of the dioxazolones on the Cu-catalyst generates acyl nitrenes that rapidly insert into the copper acetylide Cu-C bond rather than undergoing an undesired Curtius rearrangement. For non-aromatic dioxazolones, [Cu(OAc)(Xantphos)] is a superior catalyst for this transformation, leading to full substrate conversion within 10 minutes. For the direct synthesis of N-benzoyl amidine derivatives from aromatic dioxazolones, [Cu(OAc)(Xantphos)] proved to be inactive, but moderate to good yields were obtained when using simple CuI as the catalyst. Mechanistic studies revealed the aerobic instability of one of the intermediates at low catalyst loadings, but the reaction could still be performed in air for most substrates when using catalyst loadings of 5 mol%. The herein reported procedure does not only provide a new, practical and direct route to N-acyl amidines, but also represents a new type of C-N bond formation.

show abstract

“…Amidines are useful substrates with a variety of applications. The amidine structure in 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) is used frequently as a non-nucleophilic base in synthetic chemistry, 1 and more complex amidines are even considered to be "superbases". 2 Amidines also have been used as ligands for organometallic complexes 3 and as starting material for the synthesis of N-heterocycles.…”

Section: ■ Introductionmentioning

confidence: 99%

Efficient Copper Catalyzed Multi-component Synthesis of N-acyl amidines via Acyl Nitrenes

Vliet¹,

Polak²,

Siegler³

et al. 2019

Preprint

0

View full text Add to dashboard Cite

Direct synthetic routes to amidines are desired, as they are widely present in many biologically active compounds and organometallic complexes. N-Acyl amidines in particular can be used as a starting material for the synthesis of heterocycles and have several other applications. Here, we describe a fast and practical copper catalyzed 3-component reaction of aryl acetylenes, amines and easily accessible 1,4,2-dioxazol-5-ones to N-acyl amidines, generating CO2 as the only by-product. Transformation of the dioxazolones on the Cu-catalyst generates acyl nitrenes that rapidly insert into the copper acetylide Cu-C bond rather than undergoing an undesired Curtius rearrangement. For non-aromatic dioxazolones, [Cu(OAc)(Xantphos)] is a superior catalyst for this transformation, leading to full substrate conversion within 10 minutes. For the direct synthesis of N-benzoyl amidine derivatives from aromatic dioxazolones, [Cu(OAc)(Xantphos)] proved to be inactive, but moderate to good yields were obtained when using simple CuI as the catalyst. Mechanistic studies revealed the aerobic instability of one of the intermediates at low catalyst loadings, but the reaction could still be performed in air for most substrates when using catalyst loadings of 5 mol%. The herein reported procedure does not only provide a new, practical and direct route to N-acyl amidines, but also represents a new type of C-N bond formation.

show abstract

1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU): A Versatile Reagent in Organic Synthesis

Cited by 35 publications

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DBU: A Reaction Product Component

DBU: A Reaction Product Component

Efficient Copper Catalyzed Multi-component Synthesis of N-acyl amidines via Acyl Nitrenes

Efficient Copper Catalyzed Multi-component Synthesis of N-acyl amidines via Acyl Nitrenes

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