Regioselective photochemical Diels-Alder reaction on thiophene derivatives

Dearomative Intramolecular Diels-Alder/Sulfur Extrusion Reaction of Thiophenes with Alkynes Using peri-Substituted Naphthalene as a Tether

Dearomative intramolecular Diels-Alder/sulfur extrusion reaction of thiophenes with alkynes successfully afforded fluoranthenes in moderate to excellent yields. The proximity of both reactive sites fixed at the peri-position of naphthalene would play an important role in the progress of this reaction. Tri(o-tolyl)phosphine effectively suppressed the side reactions as a sulfur scavenger.

The Many Chemists Who Could Have Proposed the Woodward-Hoffmann Rules But Didn't: The Organic Chemists Who Knew of the Smoking Guns

It is a reasonable question to ask, why, as of 1965 when the five Woodward-Hoffmann communications appeared, did no other organic chemist discover the orbital symmetry rules for pericyclic reactions? The previous two papers in this 27-paper series on the history of the Woodward-Hoffmann rules discussed the physical chemists, chemical physicists, and theoretical chemists who could have solved the pericyclic no-mechanism problem; and the organic chemists in whose laboratory many of the key hints to this problem were found but still did not solve the problem. The stories of 16 other chemists who knew of (at least portions of) the pericyclic no-mechanism problem are presented in this paper. Social, political, and scientific explanations are presented as partial rationalizations as to why none of these individuals - except Woodward with Hoffmann - solved the pericyclic no-mechanism problem.

The Many Chemists Who Could Have Proposed the Woodward-Hoffmann Rules (Including Roald Hoffmann) But Didn't: The Theoretical and Physical Chemists†

It is a reasonable question to ask, why, as of 1965 when the five Woodward-Hoffmann communication appeared, did no other physical chemist or chemical physicist or theoretical chemist discover the orbital symmetry rules for all pericyclic reactions? Two theoretical chemists - Luitzen Oosterhoff (in 1961) and Kenichi Fukui (in 1964) had discovered portions of the orbital symmetry rules; their stories appear in the papers immediately preceding this paper which is Paper 5 in a 27-paper series on the history of Woodward-Hoffmann rules. Concise yet telling stories of 19 other chemists who could have, might have, perhaps even should have discovered the Woodward-Hoffmann rules are presented with explanations as to why they did not do so. Social, political, and scientific explanations will summarize the analyses.

Mild and ligand-free palladium-catalysed Suzuki–Miyaura cross-couplings in aqueous two-phase system

Pd(OAc)2 combined with an ethanol/K2HPO4 aqueous two-phase system was developed as an inexpensive and efficient catalytic system for Suzuki–Miyaura cross-coupling. The couplings between aryl iodides and arylboronic acids proceeded smoothly in moderate to excellent yields at 60°C in the aqueous two-phase system, and aryl bromides required a higher reaction temperature (reflux at about 80°C) to improve the yield.

An Efficient One-Pot Asymmetric Synthesis of Biaryl Compounds via Diels−Alder/Retro-Diels−Alder Cascade Reactions

[reaction: see text] A single-step chirality transfer method for the synthesis of axially chiral biaryl compounds by construction of the second aromatic ring via a Diels-Alder/retro-Diels-Alder cascade reaction is reported. This methodology should find broad application in the synthesis of natural products and asymmetric catalysts.

Reactions of 1,2-Dehydro-o-carborane with Thiophenes. Cycloadditions and an Easy Synthesis of "Benzo-o-carboranes"(1)

Cycloaddition reactions of 1,2-dehydro-o-carborane with thiophene, 2,5-dimethylthiophene, 2,5-dimethylfuran, [8](2,5)thiophenophane, and [8](2,5)furanophane are investigated. In all cases, except the reaction with the thiophenophane, both 4 + 2 and 2 + 2 cycloadducts are formed, with the 4 + 2 product dominating. The 4 + 2 adducts of the thiophenes are not stable but extrude sulfur under the reaction conditions to give "benzo-o-carboranes".