Ylide compounds

Oxidative addition of dihalomethanes CH2X2 to cyclic gold(i) ylide compounds yields bicyclic compounds with a methylene bridge between two gold(m) centers.2 The two halogens can also be replaced by diphenyl-dithiophosphinate groups to give products which are kinetically stable toward reductive elimination (Equation (38)).191... 

Trialkyl(2-borylvinyl)stannanes react with sulphur bis(trimethylsilylimide) to yield heterocyclic ylide compounds, as shown in reaction 21277. 

The anionic bis-ylide compounds [R2P(CH2)2] bonded as bridging ligands (mode VI) have been extensively studied in complexes of coinage metals, mainly... 

An attempted synthesis of biotin using thiocarbonyl ylide cycloaddition was carried out (131,133,134). The crucial step involves the formation of the tetrahydrothiophene ring by [3 + 2] cycloaddition of a properly substituted thiocarbonyl ylide with a maleic or fumaric acid derivative (Scheme 5.27). As precursors of the thiocarbonyl ylides, compounds 25a, 72, and 73 were used. Further conversion of cycloadducts 74 into biotin (75) required several additional steps including a Curtius rearrangement to replace the carboxylic groups at C(3) and C(4) by amino moieties. 

Stability of both the parent system and the S- oxide is conferred by the presence of electron-withdrawing substituents on the carbon framework, especially at positions 2, 4 and 6, while electron-donating substituents on sulfur also help. Compounds (48), (49) and (50) illustrate these conclusions, as they are air-stable, isolable species (74CL1101). Exactly analogous factors acting on stability are seen with acyclic sulfonium and sulfoxonium ylide compounds. 

One possibility for these side reactions might be to form ylide compounds, as shown in Scheme 5. 

In an attempt to increase the reactivities of diarylmethylene(triphenyl)phos-phorane ylides, compounds (13) and (14) have been prepared and studied by... 

The anionic bis-ylide compounds [R2P(CH2)2] bonded as bridging ligands... 

Conversely, certain mono(ylide) complexes are accessible from the respective bis(ylide) compounds. Reaction between complexes of the type [Au(ylide)2]ClC>4 and aurates such as NR4AUX2] (X = Cl, Br, C6F5, QC affords neutral halogold and (haloaryl)gold(I)... 

As can be seen, the attack of the nucleophillic oxygen of the ylide compound to the growing carbocation chain terminates polymerization. A steric hindrance around... 

Ylides, Compounds in which an atom from group V Or VI of the periodic table, bearing a positive charge, is connected to a carbon atom carrying an unshared pair of electrons. Ref A. William Johnson, Ylid Chemistry (Academic Press, New York, 1966) B, M, Trost, L, S, Melvin, Sulfur Ylides (Academic Press, New York, 1975) J. March, Advanced Organic Chemistry (McGraw-Hill, New York, 2nd ed 1977) p 40. 

Phosphonium ylides - Compounds having the structure RjP -C Rj R3P=CR2. Also known as Wittig reagents. [5]... 

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