2,5-Bis(trifluoromethyl)-1,3,4-oxadiazole

Warrener, Ronald N.

doi:10.1002/047084289x.rn00255

Cited by 2 publications

(3 citation statements)

References 32 publications

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“…In the case of C-bridged alkenes, specifically the exo,exo-product was obtained [7]. Eight different approaches of the two reactants are feasible.…”

Section: Tandem Cycloadditions Of 134-oxadiazolesmentioning

confidence: 99%

“…In a single reaction pot, two cycloaddition steps take place consecutively, new bonds are made in a process, in a continous sequence of reactions, without isolation of intermediates. Tandem [4+2]/[4+2] reactions used in the synthesis of [n]polynorbornanes include small heterocycles such as 1,2,4,5-tetrazine, [3,4] 1,2,4-triazine [3], and phthalazine [5], while tandem [4+2]/[3+2] cycloadditions use 1,3,4-oxadiazoles [6,7]. Important groups of tandem cycloaddition reactions are [4+2]/[4+2] and [4+2]/[3+2] reactions.…”

Section: Introductionmentioning

confidence: 99%

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Tandem [4+2]/[3+2] Cycloadditions of 1,3,4-Oxadiazoles with Alkenes

Margetić¹,

Trošelj²,

Johnston

2011

MROC

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A review on the tandem [4+2]/[3+2] cycloaddition reactions of 1,3,4-oxadiazoles with alkenes is presented. This reaction presents a powerful synthetic tool in the construction of complex polycyclic molecules in a one-pot reaction. Special attention is paid to synthesis of [n]polynorbornane and oxanorbornyl systems. In continuation, a review on the 1,3,4-oxadiazole reactions used in stereoselective total synthesis of alkaloids is given. Both intermolecular and intramolecular tandem [4+2]/[3+2] reactions are discussed. Stereospecificities and mechanistic rationale of various reactions are supported by quantum-chemical calculations (RHF/6-31G*). TANDEM [4+2]/[3+2] CYCLOADDITION REACTIONS OF OXADIAZOLES WITH ACYCLIC ALKENESVasil'ev reported that a series of polyfluorinated 1,3,4oxadiazoles 1-4 undergo a tandem [4+2]/[3+2] cycloadditions with acyclic alkenes, representative examples are given in Scheme 3.[15] Ethylene reacts in a sealed vessel at 200-220 o C with OD producing 1,4-bis(trifluoromethyl)-7-oxabicyclo[2.2.1]heptane 5 in 41% yield. Stereochemical or regiochemical factors come into play when the alkene bears substituents. Both regio-isomers (2,5-, 2,6-) and stereo-isomers (exo-, endo-) are then possible. The regiochemical outcome depends on the size of the substituent rather than its electronic properties. Thus, the reaction of propylene, ethyl vinyl ether, ethyl acrylate, methyl metacrylate, and isoprene give mixtures of the 2,5-and the 2,6-isomers 9-13 in each case, whereas reaction with styrene regiospecifically gave product 14. TANDEM [4+2]/[3+2] CYCLOADDITION REACTIONS OF OXADIAZOLES WITH CYCLIC ALKENESA range of cycloalkenes have been found to react with OD to form highly symmetrical coupled products 15 (n=1,2,3,5), in which the rings were exo-fused to the 7-oxanorbornane subframe (Scheme 4) [18].Reaction with cyclopentadiene proceeds in relatively mild conditions, while cyclopentene, cyclohexene and 1,4-cyclohexadiene require more drastic conditions, heating at 140-200 o C (Scheme 5) N N

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“…In the case of C-bridged alkenes, specifically the exo,exo-product was obtained [7]. Eight different approaches of the two reactants are feasible.…”

Section: Tandem Cycloadditions Of 134-oxadiazolesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tandem [4+2]/[3+2] Cycloadditions of 1,3,4-Oxadiazoles with Alkenes

Margetić¹,

Trošelj²,

Johnston

2011

MROC

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show abstract

“…A crucial step in the building BLOCK protocols is the connection of two alkene (norbornene) units utilizing cycloaddition reactions. Either Diels-Alder or 1,3-dipolar cycloadditions of small heterocyclic molecules, such as 1,2,4,5-tetrazine [7,8], 1,2,4-triazine [7], 1,3,4-oxadiazole [9,10], phthalazine [11], bis-epoxide [12], or bis-aziridine [13] were used. Using these protocols, a number of functionalized hetero-bridged and polarofacial [n]polynorbornanes was prepared [3,12,14,15].…”

Section: Introductionmentioning

confidence: 99%