Alkylidene compounds

High vacuum sublimation of the 3-monobenzoate of (32) or tosylchloride dehydration gives 3/ -benzoyloxy-7-methylenecholest-5-ene (33). The configuration of (32) is probably as shown since 7a-hydroxy steroids dehydrate readily to yield homoannular dienes. In an analogous reaction ethyl and iso-butyl Grignard reagents give alkylidene compounds as the only isolated products. 

Aspects of the apparatus for the synthesis using metal atoms are described. The reactions of the atoms of rhenium, tungsten, and osmium with hydrocarbons including alkanes are described. It is shown that metal atom reactions with alkanes can give isolable organometallic compounds including l-alkylidene compounds. 

Further analysis of the spectral data for the P2"acetyl compounds 28 and 29 (Table 1) also indicates that the positive charge is distributed over both metal centers. The electronic environment of the C-bonded iron of 28 and 29 clearly lies intermediate between that of the starting acetyl complex and of the a-alkoxy-alkylidene compounds. Similarly the acetyl complexes provide more electron density to CpFe(CO)2+ within 28 than does acetone or THF within CpFe(C0)2Li+ [L =acetone, THF]. 

Alkylidene carbonyl iridium complexes, reactions, 7, 275 Alkylidene compounds, NLO properties, 12, 121 Alkylidene-containing complexes, in molybdenum complexes, Schrock-type complexes, 5, 524 a-Alkylidene cyclic carbonyl compounds, isomerization,... 

Under the reaction conditions for alkylidenation, compounds containing the following functional groups were found to be stable trimethylsilyl ethers of alcohols, olefins, primary alkyl iodides, and ethylene acetals of aldehydes. 

The difference is interestingly exemplified in the differing modes of reaction of hydrazoic acid with some alkylidene (and arylidene) oxazolone derivativesThe alkylidene compound 174 behaves as an a, -unsaturated carbonyl compound with the hydrazoic acid adding to the exocyclic double bond. A subsequent ring opening with further addition leads to the formation of the diazide 175 (equation 75). In contrast the exocyclic double bond of the arylidene compound 176 is unreactive, and nucleophilic attack occurs at the... 

The reduction of Cp2TiCl2 with allyllithium generates alkylidene species as intermediate species in the preparation of vinylcyclopropanes (see Section 4.05.4.2.4 alkylidene compounds).1140... 

The lithium dianion of 2,4-oxazolidinedione (122) reacts with a-halo ketones to give alkylidene compounds that can be transformed into 3,5-dihydroxy-2(5fl)-furanones (123) by oxidation, followed by hydrolysis (Scheme 47) <92JOC4558>. 

Sodium borohydride reduction of either 3-acetyl- or 3-benzoyl-4-hydroxy-2H-l,2-benzothiazine 1,1-dioxides (e.g., 21, 89, 93) produced the corresponding 3-alkylidene compounds 108.4 Evidently the intermediate alcohols are dehydrated under the conditions of the reaction. The authentic ben-zylidene derivative 108 (R1 = Ph, R2 = Me), prepared4 by another route (Eq. 20), was identical to the product isolated from the borohydride reduction of compound 107. 

Although the reaction of barbiturates with saturated aldehydes normally yields the alkylidene compounds (Section III,A), condensation of 143 (R = R = H, Me) with both enantiomers of 144 produced optically pure tricyclic dihydropyrans399 (Eq. 9). 

C—C bond-forming reactions of Irm alkenyls and nitriles or aldehydes Generation of reactive hydride- and alkyl-alkylidene compounds and observation of a reversible 1,2-H shift in stable hydride-Irm alkylidene complexes... 

The ferrocenyldiphosphine ligand 99 constitutes a catalytic system with (cod)2RhBp4 for synthesizing a-alkylsuccinic acid derivatives from the alkylidene compounds. Secondary acetates in chiral form are accessible from hydrogenation of enol acetates using the catalytic system of (cod)2RhBF4-100. ... 

Understanding the role of orbital interactions can be beneficial from the practical perspective. For example, the symmetry of frontier molecular orbitals can explain why thermal [2+2] cycloaddition fails, whereas the analogous reaction of transition metal alkylidenes, compounds that can be described as having a metal-carbon double bond, proceeds efficiently under mild conditions (Figure 1.2). In this case, an extra orbital... 

Ruthenium alkylidene compounds bearing two imidazol-2-ylidene ligands (6) have also been prepared and, in olefin metathesis, they exhibit a catalytic activity comparable to that of the... 

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