Synthesis and properties of 2-trifluoromethyl-substituted 4-pentenoic and 3,4-pentadienoic acids and their esters

Андреев, В. Г.; Kolomiets, A. F.; Фокин, А. В.

doi:10.1007/bf00959719

Russ Chem Bull

1991

DOI: 10.1007/bf00959719

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Synthesis and properties of 2-trifluoromethyl-substituted 4-pentenoic and 3,4-pentadienoic acids and their esters

В. Г. Андреев

A. F. Kolomiets

А. В. Фокин

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2005

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“…The protic and Lewis acid (silver salts or BF 3 ) catalysed 5-endodig and 6-endo-dig cyclisation of aand b-allenic alcohols to 2,5-dihydrofurans and 3,6-dihydro-2H-pyrans have been described (see[55 ± 57]). The HgO-or Pd(PPh 3 ) 4 -catalysed allenol cycloisomerisation gave endo-[58] [59] and exocyclic enol ethers[60] 9. ) A 5-exo-dig cyclisation, followed by migration of the double bond, or a 5-endo-dig cyclisation appears more probable than isomerisation to the corresponding triynol, followed by a 5-exo-dig cyclisation, considering that distillation of pent-4-yn-1-ol (possessing an isolated, non-activated CC bond) in the presence of a catalytic amount of NaNH 2 gave 2-methylideneoxolane [61][62].…”

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Functionalised Bicyclic exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy 1,3‐Diynes and Hydroxy Haloalkynes

Miao

Hoffmann

et al. 2005

Helvetica Chimica Acta

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mit den besten W¸nschen herzlich zugeeignet.Functionalised bicyclic exo-glycals are readily obtained by base-catalysed (typically MeONa in MeOH) alkynol cycloisomerisation of ethynylated cyclic saccharides. Thus, base treatment of the phenylethynyl-and halogenoethynylated 1-O-acetyl-ribofuranoses 22 ± 24 and the 4-ethynylated 1-thioglucopyranosides 30 ± 33 gave ± after deacetylation ± selectively the (Z)-configured exocyclic enol ethers 26 ± 28 (84 ± 91%) and 34 ± 37 (63 ± 76%), respectively, resulting from a trans-5-exo-dig cyclisation. The ring closure to the trans-dioxahexahydroindans 34 ± 37 is favoured by a concerted intramolecular protonation of the intermediate vinyl anion by the neighbouring HOÀC(3). Cycloisomerisation of the 6-O-acetyl-4-(phenylethynyl)-1-thio-a-d-glucopyranoside 39 occurred via the corresponding phenylethynylated allenes to provide the galacto-configured (Z)-and (E)-cis-dioxahexahydroindans 40 (30%) and 41 (51%). Surprisingly, the HOÀC(4) unprotected a-dgalactopyranosyl-buta-1,3-diyne 15 and the b-d-glucopyranosyl-buta-1,3-diyne 51 (and its 2-bromoethynyl analogue) undergo a 6-exo-dig ring closure to the 2,5-dioxabicyclo[2.2.2]octanes 16 ± 19 and 52/53, respectively, the ring closure requiring a boat conformation (B 1,4 for 15, 1,4 B for 51). Ring strain (anti-reflex effect) prevents an alkynol cycloisomerisation of 4-(phenylbuta-1,3-diynyl, bromoethynyl, or iodoethynyl)levoglucosan 56 ± 59, and 56 reacted by elimination to the hex-1-ene-3,5-diyne 59 (82%), while isomerisation of 57 and 58 led to epimeric mixtures of the haloallenes 60 (82%) and 61 (68%).Introduction. ± exo-Glycals are versatile synthetic intermediates used for the preparation of, e.g., ulosides [1 ± 3], substituted endo-glycals, and functionalised Cglycosides; their chemistry has recently been summarised by Taillefumier and Chapleur [4] 1 ). Methods for the synthesis of exo-glycals comprise the Wittig-type olefination of glyconolactones and glycosylphosphonium salts, the methylenation of glyconolactones with Tebbe and Petasis reagent, addition ± elimination reaction, reductive elimination of ketopyranosyl bromides, cyclisation of ethenylated alditols induced by electrophiles, followed by elimination, and the Ramberg ± B‰cklund rearrangement of glycosyl sulfones.While alkynol cyclisation (cycloisomerisation) has been used as early as 1959 for the structure elucidation of hydroxylated oligoacetylenes, as illustrated by the highyielding cyclisation of 1 to 2 [9] [10] (Scheme 1), this facile cyclisation has, surprisingly, not been used for the transformation of carbohydrates into exo-glycals, nor has the high yielding base-or Ag

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confidence: 99%

Functionalised Bicyclic exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy 1,3‐Diynes and Hydroxy Haloalkynes

Miao

Hoffmann

et al. 2005

Helvetica Chimica Acta

View full text Add to dashboard Cite

show abstract

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Synthesis and properties of 2-trifluoromethyl-substituted 4-pentenoic and 3,4-pentadienoic acids and their esters

Cited by 1 publication

References 2 publications

Functionalised Bicyclic exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy 1,3‐Diynes and Hydroxy Haloalkynes

Functionalised Bicyclic exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy 1,3‐Diynes and Hydroxy Haloalkynes

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