Methylenation of carbonyl groups

Metalations with organolithium compounds, 8, 6 26, 1 27, 1 Methylenation of carbonyl groups, 43, 1 Methylenecyclopropane, in cycloaddition reactions, 61, 1... 

Cerium(IV) ammonium nitrate, 67 Methylation (see also Alkylation) Dimethyl sulfate, 239 Trimethyloxonium tetrafluoroborate, 327 Methylenation of carbonyl groups... 

Tributyl(iodomethyl)tin, 314 By methylenation of carbonyl groups Ix-Chlorobis(cyclopentadienyl)-(dimethylaluminum)-jx-methyl-enetitanium, 71... 

Methylenation of carbonyl groups from aldehydes, ketones, esters, lactones, amides by Ti reagents (see 1 st edition). 

The methylenation of carbonyl groups using diiodomethane was attempted but met only with a limited successP Aldehydes provide olefins in good yields, and ketones remain unchanged. The sonication conditions should be systematically investigated to base a synthetic method on these preliminary results. 

Ketones on reaction with Simmons-Smith reagent results in methylenation" of carbonyl group (Scheme 26). Normally such methylenation of carbonyl group requires complex reagents. It can now be accomplished by sonication. 

Reduced titanium species are particularly useful for promoting coupling reactions of ketones [65, 69] and methylenation of carbonyl groups, the active species in the coupling reaction are low valent Ti species (See also 7.2.2.). Organo Zr reagents couple readily with jr-allyl Pd species [59]. 

Several methods are available for reductive removal of carbonyl groups from organic compounds. Reduction to methylene groups or conversion to alkenes can be achieved. 

Zinc and hydrochloric acid form a classical reagent combination for conversion of carbonyl groups to methylene groups, a reaction known as the Clemmensen reduction 12 The corresponding alcohols are not reduced under the conditions of the... 

The Wolff-Kishner reaction175 is the reduction of carbonyl groups to methylene groups by base-catalyzed decomposition of the hydrazone of the carbonyl compound. It is thought that alkyldiimides are formed and then collapse with loss of nitrogen.276... 

Lead tetraacetate can effect oxidation of carbonyl groups, leading to formation of a-acetoxy ketones,215 but the yields are seldom high. Boron trifluoride can be used to catalyze these oxidations. It is presumed to function by catalyzing the formation of the enol, which is thought to be the reactive species.216 With unsymmetrical ketones, products from oxidation at both a-methylene groups are found.217... 

Second, titanium-based reagents are suitable for methylenation or alkylidenation of carbonyl groups of carboxylic acid derivatives such as esters and amides (Equation (7)). ... 

From reduction of carbonyl groups or masked carbonyls to methylene groups... 

In 1953 Wittig and Geissler (100) reported that methylene triphenyl-phosphorane reacted with benzophenone to form 1,1-diphenylethene and triphenylphosphine oxide. This experiment marked the birth of the Wittig reaction, a novel method for the conversion of carbonyl groups to olefins, and the entry of ylides into the arsenal of important synthetic tools. Since... 

Reduction of carbonyl group to methylene via thioacetals In contrast to the Clemmensen reduction (section 6.4.3) and Wolff-Kishner reduction (section 6.4.4), this method does avoid treatment with strong acid or base but requires two separate steps. The first step is to convert the aldehyde or ketone into a thioacetal. The second step involves refluxing an acetone solution of the thioacetal over a Raney nickel. This reduction method is known as Mozingo reduction. Hydrazine can also be used in the second step. 

The open chain structure (X) is formed in the condensation of diacylamine groups. The JV-acyllactam growth centres can undergo condensation at the cyclic as well as exocyclic methylene and carbonyl groups... 

Most allylic oxidations of methylene to carbonyl groups are carried out by chromic oxide [552, 555] or its complexes with pyridine [593, 606] and performed on steroidal esters [552, 593, 606] and ketones [61, 552] (equation 130). 

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