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

Miao, Zhiwei; Xu, Ming; Hoffmann, Barbara; Bernet, Bruno; Vasella, Andrea

doi:10.1002/hlca.200590145

Cited by 30 publications

(10 citation statements)

References 79 publications

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“…The same configuration of the C=C bond of 4 and 6 is revealed by similar chemical shifts for HÀC (5), HÀC(6), C(5), and C(6) of 4 and the corresponding 1 H-(Dd 0.06 ppm) and 13 C-NMR (Dd 0.6 ppm) signals of 6. The (Z)-configuration of 4 is suggested by similar d values for the enol ether 13 C s of 4 and of a closely related bicyclic (Z)-configured analogue [1] (163.0 vs. 164.2 ppm) differing clearly from that of the corresponding (E)-isomer (168.8 ppm) 1 ).…”

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confidence: 81%

“…-We have recently reported our investigations on the base-promoted alkynol cycloisomerisation of buta-1,3-diynlated and haloethynylated glycopyranosyl and -furanosyl alcohols to bicyclic exo-glycals [1]. In this paper, we describe the results of the alkynol cycloisomerisation of buta-1,3-diynlated, bromo-, and (pyridin-2-yl)ethynylated alditols to monocyclic exo-glycals of different ring size.…”

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confidence: 95%

“…To learn about the dependence of the alkynylation and cycloisomerisation on the configuration of the starting materials, we planned to study the transformations of galacto-, gluco-, and manno-isomers. 1 ) C(2) of (Z)-and (E)-2-methyleneoxolanes shows the same relative chemical shift as C(1) of (Z)-and (E)-lactone oximes and hydrazones [17 -19]. 2 ) The crystallographic data have been deposited with the Cambridge Crystallographic Data Centre as deposition No.…”

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Functionalised Monocyclic Five‐ to Seven‐Membered exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy Buta‐1,3‐diynes and 1‐Haloalkynols

Xu¹,

Miao²,

Bernet³

et al. 2005

Helvetica Chimica Acta

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Dedicated to András Lipták on the occasion of his 70th birthday Base-promoted (KOH or MeONa in MeOH, or NaH in THF) cycloisomerisation of partially benzylated, 1-substituted (R = PhÀCC, pyridin-2-yl, or Br) ald-1-ynitols leads to (Z)-configured five-, six-, and seven-membered exo-glycals. The reactivity of the ald-1-ynitols depends upon their configuration. The ald-1-ynitols were derived from 2,3,5-tri-O-benzyl-D-ribofuranose 1, and the corresponding, partially O-benzylated galactose, glucose, and mannose hemiacetals by ethynylation. The hex-1-ynitol 2 derived from 1 (61%) was transformed via the 1-phenylbuta-1,3-diyne 3 and the 1-(pyridin-2-yl)acetylene 5 into the five-membered exo-glycals 4 and 6 (in 66 and 72% yields, resp., from 2). The analoguous ethynylation of 2,3,4,6-tetra-O-benzyl-D-galactose 8 was accompanied by elimination of one benzyloxy (BnO) group to the hept-3-en-1-ynitol 9 (71%), which was transformed into the non-5-ene-1,3-diynitol 10 and further into the six-membered exo-glycal 11 (50% from 9). Addition of Me 3 SiCCH to the galactose 8 and to the gluco-and manno-analogues 16 and 24 gave epimeric mixtures of the silylated oct-1-ynitols (86% of 12L/12D 45 : 55, 94% of 17L/17D 7 : 3, and 86% of 25L/25D 55 : 45), which were separated by flash chromatography, and individually transformed into the corresponding 1-bromooct-1-ynitols. Upon treatment with NaH in THF, only the minor epimers 13L, 18D, and 26D cyclised readily to form the seven-membered hydroxy exo-glycals. They were acetylated to the more stable monoacetates 14L, 23D, and 28D (82 -89% overall yield). Under the same conditions, the epimers 13D, 18L, and 26L decomposed within 12 h mostly to polar products. The difference of reactivity was rationalised by analysing the consequences of an intramolecular C(3)OÀH ··· À OC (7) H-bond of the intermediate alkoxides on the orientation of À OÀC(7) of 13L, 18D, and 26D and its proximity to the ethynyl group.Introduction. -We have recently reported our investigations on the base-promoted alkynol cycloisomerisation of buta-1,3-diynlated and haloethynylated glycopyranosyl and -furanosyl alcohols to bicyclic exo-glycals [1]. In this paper, we describe the results of the alkynol cycloisomerisation of buta-1,3-diynlated, bromo-, and (pyridin-2-yl)ethynylated alditols to monocyclic exo-glycals of different ring size.In the course of the structure elucidation of naturally occurring oligoacetylenes, Jones et al. [2] and Bohlmann et al.[3] discovered the base-catalysed 5-exo-dig cyclisation of hydroxylated oligoacetylenes to 2-methylidene-oxolanes. This alkynol cycloisomerisation is favoured when the alkynyl group is activated, as in cumulated triple bonds, or by substitution with a 1-bromo, 1-chloro, 1-phenylchalcogeno (S or Se), or 1-(het)aryl group, and also by the proximity of the reacting groups, as in cyclic starting materials [1] [4 -6]. Activation of an isolated alkynyl group by coordination with a Lewis acid also promotes the cycloisomerisation [7]. In most cases, cyclosiomerisation resulted in (Z)-co...

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Functionalised Monocyclic Five‐ to Seven‐Membered exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy Buta‐1,3‐diynes and 1‐Haloalkynols

Xu¹,

Miao²,

Bernet³

et al. 2005

Helvetica Chimica Acta

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“…4 Kcal/mol), with the fusion of the side tetrahydropyrane rings to rigid scaffolds suppressing the conformational equilibrium between both isomers. In addition to the gold-catalyzed reactions just commented on, several works describing the base-promoted cyclization of 1,3-diynic substrates bearing tethered hydroxyl groups can be found in the literature [166][167][168][169][170][171][172]. A couple of illustrative examples are given in Scheme 64 [172].…”

Section: Hydroalkoxylation Processesmentioning

confidence: 99%

Catalytic Hydrofunctionalization Reactions of 1,3-Diynes

Cadierno

2022

Catalysts

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Metal-catalyzed hydrofunctionalization reactions of alkynes, i.e., the addition of Y–H units (Y = heteroatom or carbon) across the carbon–carbon triple bond, have attracted enormous attention for decades since they allow the straightforward and atom-economic access to a wide variety of functionalized olefins and, in its intramolecular version, to relevant heterocyclic and carbocyclic compounds. Despite conjugated 1,3-diynes being considered key building blocks in synthetic organic chemistry, this particular class of alkynes has been much less employed in hydrofunctionalization reactions when compared to terminal or internal monoynes. The presence of two C≡C bonds in conjugated 1,3-diynes adds to the classical regio- and stereocontrol issues associated with the alkyne hydrofunctionalization processes’ other problems, such as the possibility to undergo 1,2-, 3,4-, or 1,4-monoadditions as well as double addition reactions, thus increasing the number of potential products that can be formed. In this review article, metal-catalyzed hydrofunctionalization reactions of these challenging substrates are comprehensively discussed.

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“…Under these conditions, the reaction time could be reduced from 4.5 to 1.5 h. Deprotection with in situ generated Me 3 SiBr in MeCN gave pteridinedione 25. Treating 11 with phenyl 2,3,6-tri-O-acetyl-4-deoxy-4-ethynyl-1-thio-b-d-glucopyranoside [15] [16] under conditions of the Sonogashira reaction gave the 6-ethynylpteridine 26. It was isolated in 89% yield by silica-gel chromatography.…”

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confidence: 99%

Acylation of a 6‐(Methylamino)‐5‐nitrosopyrimidine and 1,3‐Dipolar Cycloaddition of an 8‐Methylisoxanthopterin N(5)‐Oxide. Synthesis of C(6),N(8)‐Disubstituted Isoxanthopterins

Steinlin

Vasella

2009

Helvetica Chimica Acta

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Acylation of 2-amino-4-(benzyloxy)-6-(methylamino)-5-nitrosopyrimidine (5) with acetic anhydride or chloroacetic anhydride in the presence of 4-(dimethylamino)pyridine (DMAP) led to the C(2)-acylamino derivatives 6 and 7, respectively. In the absence of a base, acetylation did not lead to a product, while chloroacetylation led to the 6-chloropteridine 11. Chloroacetylation in the presence of Hünigs base provided the pteridinone N(5)-oxide 10, suggesting that acylation of 5 is readily reversible, and that the unfavourable equilibrium must be displaced by a follow-up reaction to trap the acylation product. Acylation of 5 with hexadienoyl chloride, followed by intramolecular Diels -Alder reaction, provided the pteridinone 12. A high yielding 1,3-dipolar cycloaddition of the acylnitrone 10 to electron-poor and electron-rich dipolarophiles, followed by spontaneous N,O-bond cleavage, gave the C(6)-substituted pteridinones 19a -19e that were deprotected to the pteridine-4,7(3H,8H)-diones 20a -20e. Substitution of the 6-chloropterin 11 provided the 6-morpholinopteridine 25. Sonogashira coupling yielded the fluorescent [(pteridin-6-yl)ethynyl]-glucopyranoside 26, 6-ethynylpteridine 28, and 6,6'-(ethynediyl)-bispteridine 29. The alkyne 28 reacted with Me 3 SiCl and LiBr in MeCN to produce the bromoalkene 31.Introduction. -We described new routes to 6-substituted pteridines based on intramolecular Diels -Alder cycloadditions, ene-reactions, and condensations of N(6)-acylated or N(6)-alkylated 6-amino-5-nitrosopyrimidines [1 -4]. We also showed that the pteridinone N(5)-oxides, resulting from the condensation of 6-amino-5-nitrosopyrimidines with chloroacetic acid anhydride ((ClCH 2 CO) 2 O) react as acylnitrones. The course of their [3 þ 2] cycloaddition to acceptor-substituted dipolarophiles is illustrated in Scheme 1 by the addition of 1 to methyl acrylate. This reaction provides 2, resulting from a spontaneous eliminative cleavage of the N,O bond of the initially formed isoxazolidine, and thus constitutes a new, high-yielding access to isoxanthopterins 2 possessing a functionalised side chain at C(6) [5]. The poor solubility of these isoxanthopterins was assumed to result from a favourable intermolecular H-bonding of the DADA motif involving HN(2'), N(1'), HN(8') and O¼C(7') of the products of type 2. This hypothesis prompts to investigate the formation and 1,3-dipolar cycloaddition of N(8)-alkyl derivatives of 1. The simplest ones, N(8)-methylpteridinone N(5)-oxides, should be obtained by an intramolecular condensation of 6-[(chloroacetyl)(methyl)-amino]-5-nitrosopyrimidines. We were thus interested in the cycloaddition of N(8)-alkylated pteridinone N(5)-oxides and the solubility of the resulting products, in the formation of the pteridinone N-oxides by condensation of 6-[(alkyl)(chloroacetyl)-amino]-5-nitrosopyrimidines, and in the N-acylation leading to these amides. As we had

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

Cited by 30 publications

References 79 publications

Functionalised Monocyclic Five‐ to Seven‐Membered exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy Buta‐1,3‐diynes and 1‐Haloalkynols

Functionalised Monocyclic Five‐ to Seven‐Membered exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy Buta‐1,3‐diynes and 1‐Haloalkynols

Catalytic Hydrofunctionalization Reactions of 1,3-Diynes

Acylation of a 6‐(Methylamino)‐5‐nitrosopyrimidine and 1,3‐Dipolar Cycloaddition of an 8‐Methylisoxanthopterin N(5)‐Oxide. Synthesis of C(6),N(8)‐Disubstituted Isoxanthopterins

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