Bismuth(III) salts as synthetic tools in organic transformations

Bismuth is the heaviest stable element of the periodic table and even though it carries the status of heavy metal, it is rated as relatively nontoxic and noncarcinogenic unlike its neighboring elements. Additionally, the fact that it tolerates air and moisture makes the chemistry of bismuth attractive to synthetic chemists. The catalytic nature of this metal is attributed to the capability of its salts to acts as Lewis acids in reactions. The nontoxicity together with the ability to endure moisture makes bismuth compounds favorites of chemists and scientists who are concerned about environmental hazards, and such properties are highly desirable for scale-up of a method. The Lewis acidic nature of salts of this element have been thoroughly investigated in various types of reactions such as cycloaddition reactions, reactions of sugars, protection and deprotection reactions, synthesis of heterocyclic systems etc. Since the 1990s, various research groups have successfully utilized this catalytic nature for many organic transformations. Our group's contribution towards the development of methodologies that are useful in accomplishing various functional group manipulations by making use of the catalytic properties of bismuth salts is portrayed here. The mechanistic aspects and the catalytic efficiency of the bismuth(III) salts are accented together with the synthetic utility and the biological and pharmacological applications of the methodologies developed.

Total synthesis of the tropoloisoquinoline alkaloid pareitropone via alkynyliodonium salt chemistry and related studies

The first chemical synthesis of pareitropone, by a route featuring application of alkynyliodonium salt chemistry, is described. The key transform initiates with addition of an alkylidenecarbene, derived by intramolecular nucleophile addition to the alkynyliodonium moiety, to a proximal aromatic ring. This addition delivers a highly strained norcaradiene substructure that rapidly reorganizes to furnish the pareitropone skeleton.

Alkynyliodonium Salts in Organic Synthesis. Application to the Total Synthesis of the Tropoloisoquinoline Alkaloid Pareitropone

The synthesis of the tropoloisoquinoline alkaloid pareitropone has been accomplished in 14 steps from 2,3,4-trimethoxybenzoic acid. The key transformations include the generation of an alkylidenecarbene intermediate through intramolecular addition of a tosylamide anion to an alkynyliodonium salt, and the cycloaddition of that carbene to a peri positioned aromatic ring to afford a cycloheptatrienylidene product featuring the intact pareitropone skeleton.

New cyclohexadienone derivatives: preparation and chiral discrimination in high-pressure Diels-Alder cycloadditions

A wide range of cyclohexadienones has been synthesised in order to study their reactivity and their regio- and stereoselectivity with the enantiopure diene 1 under high-pressure conditions. Computational investigations were used to point out some parameters which affect the reactivity in this high chiral discrimination process. In addition, the resulting [4+2] cycloadducts allowed the preparation of new polyfunctional cyclohexenone derivatives.

Regioselective intramolecular oxidation of phenols and anisoles by dioxiranes generated in situ

A novel method for regioselective oxidation of phenols and anisoles has been developed in which dioxiranes, generated in situ from ketones and Oxone, oxidize phenol derivatives in an intramolecular fashion. A series of ketones with electron-withdrawing groups, such as CF(3), COOMe, and CH(2)Cl, were attached to phenols, anisoles, or aryl rings via a C(2) or C(3) methylene linker. In a homogeneous solvent system of CH(3)CN and H(2)O, oxidation of phenol derivatives 1-10 afforded spiro 2-hydroxydienones in 24-55% yields regardless of the presence of other substituents (ortho Me, meta Me or Br) on the aryl ring and the length of the linker. Experimental evidences were provided to support the mechanism that involves a regioselective pi bond epoxidation of aryl rings followed by epoxide rearrangement and hemiketal formation.

Quinone Alkylation Using Organocadmium Reagents: A General Synthesis of Quinols

Reactions of p-benzoquinone with organocadmium reagents yield quinols, the result of quinone carbonyl monoalkylation. The reactions proceed in good yield and are devoid of bisaddition and hydroquinone byproducts. Quinone alkylations using this method show general applicability to p-benzoquinone as well as extended quinone systems using primary alkyl, secondary alkyl, and aryl reagents.