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•Brønsted acid-induced one-pot synthesis of 2-methylbenzofurans.•Construction of new C–O bond formation via an efficient Grob-type fragmentation.•Halobenzofurans were successfully ...utilized to synthesis 6,7-bisaryl benzofurans.
An efficient Brønsted acid-induced one-pot syntheses of 2-methylbenzofurans from norbornyl derivatives have been reported. The construction of new C–O bond proceeds via Grob-type fragmentation followed by cyclization and aromatization respectively. This synthetic strategy facilitates the efficient synthesis of 2-methylbenzofurans under acidic conditions. Significantly, this methodology is successfully applied to the synthesis of 6,7-bisaryl benzofurans.
A general approach toward the synthesis of multi-functionalized diazapentacene derivatives 1, using 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene (TDCp, 2), a substituted benzene-1,2-diamine (ADA, ...6), and a naphthalene-1,4-dione (BQ, 3) as the building units, is described. The synthesis basically entails three operations: (i) oxidation of the dichloroetheno-bridge in the Diels-Alder cycloadduct 4 of TDCp and 3, (ii) condensation of the 1,2-diketone 5 thus generated with an ADA to give quinoxaline-fused polycyclic compounds 7, followed by (iii) an one-pot, three-reaction process keyed upon the base- or acid-catalyzed aromatization-driven Grob-type fragmentation to produce quinoxaline ring-embedded diazapentaceneesters 1. The diazapentacene derivative 1a underwent the nucleophilic aromatic ipso-amination with primary and secondary amines to afford the amino-substituted derivatives 12, which tend to self-assemble in solid state driven by the cofacial π-stacking interactions, demonstrated by the crystal packing structures of 12a and 12f.
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•The multi-functionalized diazapentacene derivatives 1 can be synthesized by a general and flexible approach, using 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene, a substituted benzene-1,2-diamine, and a naphthalene-1,4-dione as the building units.•The diazapentacene derivatives 1 have an electronic structure exhibiting high electron affinity and are good candidates for n-type semiconducting material.•The diazapentacene derivatives 1 undergo the ipso-amination with electron-donating primary and secondary amines as nucleophiles, paving the way for exploring prospective application of synthesizing the D–π–A molecules (push–pull systems).
A trans‐selective access to enol ethers with a disubstituted C=C bond was developed. It consists of a diastereoselective glycolate aldol addition, a hydrolysis, and a Grob fragmentation. Aldol ...additions of N‐(benzyloxy)acetyloxazolidinones furnished syn‐aldols selectively. Hydrolytic removal of the auxiliaries gave α‐benzyloxy‐β‐hydroxycarboxylic acids. Exposure to DMF dineopentylacetal induced Grob fragmentations, which delivered trans‐configured enol ethers. Applying our 3‐step sequence in a bidirectional synthesis led to bis(enol ethers) trans,trans‐selectively, i.e., to a motif rarely encountered in the literature. A modified precursor synthesis allowed for the first time to access both the E‐ and the Z‐isomer of an enol ether with a trisubstituted C=C bond stereoselectively using a Grob fragmentation route. The Ar–Br and C≡C–SiMe2tBu motifs of appropriate enol ethers engaged in follow‐up reactions via organometallics. These provided more elaborated enol ethers.
A three‐step sequence for the stereoselective synthesis of enol ethers is reported. Diastereoselective glycolate aldol additions were used to access syn‐aldols. Their hydrolysis afforded ((beta))‐hydroxycarboxylic acids. Ensuing Grob fragmentations produced trans‐configured enol ethers. The product scope was extended to bis(enol ethers) and enol ethers with a trisubstituted C=C bond.
Synthesis of 2-Oxaadamantane Derivatives Ivleva, E. A.; Klepikov, V. V.; Khatmullina, Yu. E. ...
Russian journal of organic chemistry,
2022/1, Volume:
58, Issue:
1
Journal Article
Peer reviewed
Open access
1,3-Dichloroadamantanes in fuming nitric acid were converted to mixtures of 2-oxaadamantane derivatives whose structure was determined by two-dimensional NMR methods and X-ray analysis. The resulting ...compounds can be used in the design of highly complex molecules as subjects for studying biological activity.
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A facile and efficient base promoted one-pot dimerization of halo cyclohexene derivatives leading to a de novo synthesis of biologically important diarylmethane and diarylmethanone ...derivatives is reported. A plausible mechanism for the unexpected formation of the title compounds involves dehydrohalogenation, 1,6-conjugate addition, subsequent aromatization through C–C bond cleavage and dehydrohalogenation.
Hen or egg? The polyketide‐based p‐quinone methide antibiotic, elansolid A3, was isolated from the gliding bacterium Chitinophaga sancti. It now appears probable that elansolid A3 is the underlying ...biosynthetic product of the atropisomeric macrolide antibiotics elansolid A1 and A2 (see scheme). Under mild basic conditions the interconversion of elansolid isomers A1–A3 was observed. Under mild acidic conditions a Grob‐type fragmentation of elansolid A3 led to the p‐hydroxy styryl isomer elansolid D.
Methyl‐branched (Z)‐trisubstituted olefins are found in many polyketides with interesting biological activity, such as epothilone D (1), discodermolide (3), and peloruside A (2). Despite the ...employment of numerous different strategies, this motif has often been the weak point in total synthesis. Thus, we present a novel hydroxide‐ induced Grob‐type fragmentation as an easy access to trisubstituted olefins. In our case, β‐mesyloxy δ‐lactones with three stereogenic centers were chosen whose fragmentation underlies a high stereoelectronic control. Major challenges in the syntheses were the installation of quaternary stereocenters, achieved by enzymatic desymmetrization of meso‐diesters and by aluminium‐promoted stereoselective rearrangement of chiral epoxides, respectively. Different aldol strategies were developed for the formation of the fragmentation precursors. Additionally a short survey about nucleophilic additions to aldehydes with quaternary α‐centers is presented.
A new hydroxide‐induced decarboxylative Grob‐type fragmentation for the stereoselective synthesis of methyl‐branched trisubstituted olefins, an important motif in many polyketides with interesting biological activity, such as peloruside A, discodermolide, and epothilone D, is presented. This strategy centers on mesyloxy lactones (see scheme) with three stereogenic centers, one quaternary, which upon treatment with hydroxide fragment extrusion of the leaving group and carbon dioxide to the olefin.
A novel approach to the highly functionalized taxane ABC ring system through chemical conversion of the C
19-diterpenoid alkaloid deltaline (
1) was achieved in six steps (
1→
17) in 18% overall ...yield mainly by Grob fragmentation, fission of the Δ
9(14) double bond, followed by aldol condensation, and Pelletier's cleavage process.
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