Sulfur-assisted propargyl-allenyl isomerizations and electrocyclizations for the convenient and efficient synthesis of polyfunctionalized benzenes and naphthalenes

Nucleophilic functionalizations of indole derivatives using the aromatic Pummerer reaction

Because of the electron-rich property of indoles, direct functionalization strategies towards indoles generally involve electrophilic substitutions. In this paper, an efficient protocol for nucleophilic hydroxylation, halogenation and esterification of indoles via the aromatic Pummerer process was developed. With the advantages of readily accessible starting materials, simple operation and mild conditions, this protocol should be of interest to synthetic scientists.

Construction of 3-Sulfonyl Naphthalenes via Tandem Reaction of 1,4-Diyn-3-yl Esters with Sodium Sulfinates

Polysubstituted 3-sulfonyl naphthalenes were constructed in good to high yields by AlCl₃-mediated tandem reaction of 1,4-diyn-3-yl esters and sodium sulfinates. This reaction proceeded under mild reaction conditions and tolerated a variety of functional groups. Moreover, the mechanistic studies indicated that the initial formation of allene under DBU from 1,4-diyn-3-yl ester and a sequence of nucleophilic addition of sodium sulfinate, the formation of allene, and intramolecular cyclization might be involved.

Nucleophilic Functionalizations of Aniline Derivatives: Aromatic Pummerer Reaction for Umpolung Halogenation and Hydroxylation on Benzene Ring

In this paper, a metal-free protocol of nucleophilic ortho-halogenation and hydroxylation of anilines via an aromatic Pummerer process is reported.

Stereoselective and regioselective 5-exo-dig cyclization of 8-alkynylnaphthalen-1-amines for the synthesis of (E)-2-(arylthio)alkylene-1,2-dihydrobenzo[cd]indoles

A palladium and iodine-cocatalyzed 5-exo-dig aza-thiocyclization of 8-alkynylnaphthalen-1-amines for the synthesis of (E)-2-alkylene-1,2-dihydrobenzo[cd]indole thioethers is reported. As a result of broad reaction scope, simple operation, mild conditions, and high stereoselectivity and regioselectivity, this reaction should have potential utility in organic synthesis.

Aromatic Pummerer reaction for the remote para- or ortho-benzyl nucleophilic functionalization

The classic Pummerer reaction involves an α-substituted sulfide via an elimination/addition of a thionium ion. In this paper, we reported a remote para- or ortho-benzyl nucleophilic functionalization using an aromatic Pummerer process. A plausible mechanism involving a quinone thionium intermediate was proposed to explain this reaction.

Construction of Polysubstituted 1,2-Dihydrocyclobuta[b]naphthalenes and 1,2-Dihydrocyclobuta[b]anthracenes with Photoluminescence

A facile protocol for the synthesis of polysubstituted 1,2-dihydrocyclobuta[b]naphthalenes and 1,2-dihydrocyclobuta[b]anthracenes was developed via a sequence of base-promoted 1,5-H shift, intramolecular [2 + 2] cycloaddition, and aromatization. The synthesized 1,2-dihydrocyclobuta[b]anthracenes exhibited bright blue emissions in solution and strong yellow emissions in solid, which made them possible candidates for optoelectronic conjugated materials.

Applicable β-sulfonium carbanions: facile construction of thiophene derivatives

A sequence of Sonogashira coupling, propargyl-allenyl isomerization, intramolecular addition and [3, 3] sigmatropic rearrangement affords thiophene derivatives.

1,3-Dien-5-ynes: Versatile Building Blocks for the Synthesis of Carbo- and Heterocycles

1,3-Dien-5-ynes have been extensively used as starting materials for the synthesis of a wide number of different carbo- and heterocycles. The aim of this review is to give an overview of their utility in organic synthesis, highlighting the variety of compounds that can be directly accessed from single reactions over these systems. Thus, cycloaromatization processes are initially commented, followed by reactions directed toward the syntheses of five-membered rings, other carbocycles and, finally, heterocycles. The diverse methodologies that have been developed for the synthesis of each of these types of compounds from 1,3-dien-5-ynes are presented, emphasizing the influence of the reaction conditions and the use of additional reagents in the outcome of the transformations.

Sulfone promoted Rh(iii)-catalyzed C–H activation and base assisted 1,5-H shift strategy for the construction of seven-membered rings

A sequence of Rh(iii)-catalyzed C–H cleavage, 1,5-H shift and intramolecular allene insertion was developed for the construction of seven-membered rings.

Intramolecular C-F and C-H bond cleavage promoted by butadienyl heavy Grignard reagents

Organomagnesium compounds (Grignard reagents) are among the most useful organometallic reagents and have greatly accelerated the advancement of synthetic chemistry and related sciences. Nevertheless, heavy Grignard reagents based on the metals calcium, strontium or barium are not widely used, mainly due to their rather inert heavy alkaline-earth metals and extremely high reactivity of their corresponding Grignard-type reagents. Here we report the generation and reaction chemistry of butadienyl heavy Grignard reagents whose extremely high reactivity is successfully tamed. Facile synthesis of perfluoro-π-extended pentalene and naphthalene derivatives is realized by the in situ generated heavy Grignard reagents via intramolecular C-F/C-H bond cleavage. These obtained perfluorodibenzopentalene and perfluorodinaphthopentalene derivatives show low-lying LUMO levels, with one being the lowest value so far among all pentalene derivatives. Our results set an exciting example for the meaningful synthetic application of heavy Grignard reagents.

Molecular iodine-mediated reaction of 2-(2-phenylethynyl)-Morita–Baylis–Hillman adducts: an easy route to naphthyl ketones and iodo-substituted isochromenes

The iodine mediated reaction of 2-(2-phenylethynyl)-MBH gives corresponding naphthyl ketones and iodo-substituted isochromenes.

Cycloaromatization protocol for synthesis of polysubstituted phenol derivatives: method development and mechanistic studies

The scope of the cycloaromatization of propargylic ethers was explored using operationally simple air- and moisture-insensitive conditions. Highly substituted phenol derivatives were obtained in high yields. Mechanistic experiments indicate that the reaction occurs by an electrocyclization followed by 1,3-proton transfer.

Heteroatom as a promotor: synthesis of polyfunctionalized benzenes and naphthalenes

Construction of a new benzene via the electrocyclization of diene-allene is an efficient protocol to access polysubstituted benzenes from simple, readily available starting materials. In this paper, we present a comprehensive study of a heteroatom-promoted propargyl-allenyl isomerization and electrocyclization for the facile and efficient synthesis of polyfunctionalized benzenes and naphthalenes. As a result of the readily accessible starting materials, simple operation, and mild conditions, this reaction should be an appealing strategy in organic synthesis.