共查询到20条相似文献,搜索用时 9 毫秒
1.
A new route for the synthesis of guaiane and nor-guaiane sesquiterpenoids is described, using a ring-closing metathesis annulation reaction sequence on a chiral enantiopure cycloheptenone derived from (R)-(−)-carvone. 相似文献
2.
A synthetic strategy for ‘disarming’ a terminal alkene by substitution with a bulky silyl blocking group has been developed. In a series of model studies, sequential selective ring-closing metathesis of trienes followed by selective mono-hydrogenation of the resulting diene is described. The bulky silylated alkene is activated for a subsequent cross-metathesis reaction with a range of diverse alkenes by protodesilylation. 相似文献
3.
Base-induced coupling/cyclization stepwise [3+2] annulation of α-sulfonylacetamide with (Z)-2-bromoacrylates yielded polysubstituted pyroglutamates with three contiguous chiral centers with trans-trans orientation in a one-pot synthesis. The pyrrolizidine skeleton was obtained via the ring-closing metathesis (RCM) method. This facile strategy was used to synthesize psudoheliotridane. 相似文献
4.
Timothy F. Briggs 《Tetrahedron letters》2005,46(45):7793-7796
The hydroquinone lactone core of the floresolides was synthesized through a ring-closing metathesis (RCM) approach. Optimal RCM efficiency was obtained at higher reaction concentration. An unexpected Lewis acid-promoted rearrangement of the hydroquinone and other observations relevant to on-going total synthesis efforts are discussed. 相似文献
5.
Philip Børsting 《Tetrahedron》2006,62(6):1139-1149
Four different nucleosides with olefinic 2′-modifications were prepared; 2′-C-methylene, 2′-C-(propen-1-yl), 2′-C-allyl and 2′-O-allyl uridines, respectively. These were incorporated into dinucleotides with allyl phosphate or vinyl phosphonate linkages. Hence, six different dinucleotides were studied as substrates for RCM reactions, and from four of these, cyclic dinucleotides with connections between 2′-C and phosphorus of 3-6 atoms were obtained. 相似文献
6.
4,4-Difluoromassoialactone has been synthesized for the first time via a very short sequence, where the ring-closing metathesis (RCM) was employed as a key step. The efficient procedure can easily be extended to the synthesis of other gem-difluoromethylenated α,β-unsaturated-δ-lactone moiety. In addition, the viability of RCM of high electron-deficient olefins has been demonstrated. 相似文献
7.
Debra J. Wallace 《Tetrahedron letters》2005,46(4):591-594
A detailed study of the steps involved in the double ring-closing metathesis reaction of 2 to 3 has been carried out. Both the selectivity and mechanism were affected by choice of catalyst. 相似文献
8.
Sulfur-substituted quinolizidines and pyrido[1,2-a]azepines (7) can be prepared by ring-closing metathesis (RCM) of 4-(phenylthio)-1,2,5,6-tetrahydropyridin-2-ones (6) bearing terminal alkenyl groups at both N-1 and C-6 positions, which are obtained from 3-(phenylthio)-3-sulfolene (1) in four steps. Some synthetic transformations of 2-(phenylthio)-1,6,9,9a-tetrahydroquinolizin-4-one (7a) and 2-(phenylthio)-1,6,9,10,10a-pentahydropyrido[1,2-a]azepin-4-one (7d) are also reported. 相似文献
9.
Shiyue Fang 《Tetrahedron letters》2004,45(46):8501-8504
By connecting six terminal olefins sequentially in one molecule under metathesis conditions, three macrocycles were formed efficiently in one pot yielding a novel cryptand with tetrahedral connectivity. 相似文献
10.
Marie-Alice Virolleaud 《Tetrahedron letters》2007,48(8):1417-1420
A ring-closing metathesis (RCM)/cross-metathesis (CM) domino reaction has been applied to esters and unsymmetrical ether prepared from 1,5-hexadien-3-ol. For the first time, dihydropyran derivatives have been obtained via a regioselective cyclization. This reaction was performed in high yield and E stereoselectivity. 相似文献
11.
Daniel Rost 《Tetrahedron letters》2008,49(41):5968-5971
Highly efficient formation of tetrasubstituted olefins is described by ring-closing metathesis (RCM) using catalyst 2 in presence of hexafluorobenzene. This combination with hexafluorobenzene shows an unexpected promoting effect, which requires low catalysts loadings and allows the conversion of deficient olefins in high yields and very short reaction times. 相似文献
12.
Ian Cumpstey 《Tetrahedron letters》2005,46(37):6257-6259
(1R,2S,3S,4R)-2,3,4-Tri-O-benzyl-5-(benzyloxymethyl)-cyclohex-5-ene-1,2,3,4-tetrol, a precursor of the α-glucosidase inhibitor, valienamine, was synthesised in eight steps from tetrabenzyl glucose. The key steps were the selective protection of an open-chain diol, and the formation of the cyclohexene ring by ring-closing metathesis with the trisubstituted olefin of valienamine correctly in place. 相似文献
13.
Six to eight-membered carbocycles and eight-membered azacycles fused to the 2,3-position of the indole ring, representing tricyclic substructures of several indole alkaloids, can be synthesized by RCM reactions from easily accessible dienic precursors. 相似文献
14.
Ring-closing metathesis of dienes and enynes tethered by an N-N bond produced 6- to 10-membered cyclic 1,2-diaza compounds. The enyne RCM adducts were further transformed by Diels-Alder reaction into aromatic compounds. 相似文献
15.
Alain Hercouet 《Tetrahedron letters》2004,45(47):8749-8751
Ruthenium catalyzed ring-closing metathesis has been used as a key step for the synthesis of cyclic α-aminoboronic esters as, for example, boron-containing mimics of pipecolic, 2-azepanecarboxylic acid or baikiain. 相似文献
16.
Concise synthesis of 8-oxypseudopalmatine and 8-oxypseudoberberine has been achieved using ruthenium-catalyzed ring-closing metathesis (RCM) as the key step, in which the RCM substrates, 3-arylisoquinolinones, were prepared by lithiated cycloaddition reaction with o-toluamides and benzonitriles. 相似文献
17.
We have demonstrated a simple and an efficient method for the synthesis of spirocycles starting with inexpensive and commercially available carbonyl compounds. Various spirocycles involving spiropropellane derivative have been assembled via ring-closing metathesis with the aid of Grubbs’ first generation catalyst. 相似文献
18.
The azocino[4,3-b]indole system, tricyclic substructure of the indole alkaloids apparicine and ervaticine, is efficiently assembled by ring-closing metathesis of 2-allyl-3-(allylaminomethyl)indoles. The metathesis sites are introduced into the indole nucleus by reductive amination of a 3-formyl derivative with allylamine, followed by α-lithiation with subsequent electrophilic trapping with acrolein. 相似文献
19.
Unai Martínez-Estíbalez 《Tetrahedron letters》2007,48(16):2919-2922
Palladium-catalyzed arylation followed by Grignard addition to imines and ring-closing metathesis, using Grubbs’ catalysts, provides a route to six-, seven-, and eight-membered azabicycles. 相似文献
20.
An efficient synthesis of secosteroidal macrocycles has been achieved via an oxidative ring-expansion/ring-opening sequence and a ring-closing metathesis reaction as the key steps. 相似文献