Cyclohexane benzylidene

Incorporation of the carboxylic acid group into the substrate also had an effect on the stereochemistry of the Alder-ene products. Trost and Gelling60 observed diastereoselectivity in the palladium-catalyzed cycloisomerization of 1,7-enynes when the reactions were conducted in the presence of A,A-bis(benzylidene)ethylene diamine (BBEDA, Figure 2). They were able to synthesize substituted cyclohexanes possessing vicinal (Equation (53)) and... 

Benzylidene derivatives of the enantiomers of 1,2-diaminocyclohexane are also excellent ligands for the Cu(I)-catalyzcd asymmetric aziridination of olefins with 64, but the enantioselectivities using acyclic alkenes were about the same as those using ligand (S, S )-6658. When (5, 5 )-bis-(2,4-dichlorobenzylidenediamino)cyclohexane [(S,S)-67] was employed with C.u(I) triflate, 6-cyano-2,2-dimethylchromene (68) was converted to (R,R) 69 in a 75% yield with an ee greater than 98%58. 

J. S. Brimacombe, A. B. Foster, B. D. Jones, and J. J. Willard, Reaction of the cyclohexane-1,2-diols and methyl 4,6-0-benzylidene-a-D-gluco- and galactopyranoside with methylene halides, J. Chem. Soc. C. 2404 (1967). 

Benzylidene and isopropylidene acetals are often used for the selective protection 1,2-cis or 1,3-cisjtrans diols of sugar derivatives. They are stable to strong basic conditions but quite fragile towards acid. Recently, dispirodiketal and cyclohexane-1,2-diacetal groups have been introduced to protect selectively 1,2-trans diols of carbohydrates. 

Benzylidene and isopropylidene acetals of irons-1,2-diols are very labile as a result of ring strain and are not often used for synthetic applications. Fortunately, the protection of these diols can be accomplished with the recently developed dispiroketal (dispoke)35 and cyclohexane-1,2-diacetal (CDA) groups.36... 

Ruthenacyclopentane 331 has been postulated as an intermediate in the ruthenium-catalyzed cycloisomerization of lactones <2003TL2157>. Cycloisomerization of phenylsulfonylallenes to the cyclohexane derivatives catalyzed by a ruthenium benzylidene complex might proceed through the ruthenacyclopentane intermediate 332 <2006TL3971>. The [( 7 -Cp")RuCl( -COD)]-catalyzed cyclotrimerization of 1-octyne with dimethyl acetylenedi-carboxylate proceeds via a ruthenacyclopentadiene <2004JMO(209)35>. 

Ethyl trifluoroacetoacetate (3.0 g. 16.2 mmol) and A-(benzylidene)methylamine. V-oxide (1 2.6 g. 19.4 mmol) were refluxed in toluene for 24 h. After evaporation of the toluene, the crude product was filtered on a silica gel column, and the isoxazolidinc obtained by crystallization from cyclohexane yield 3.36 g (65%) mp 94-96 C. 

Isopropylidene (acetonides) and benzylidene derivatives are the most commonly used acetals for the simultaneous protection of 1,2- and 1,3-diols in carbohydrate and nucleoside chemistry [123]. Cyclohexylidene acetals are occasionally used, most often as an alternative to benzylidene acetals. Protection using cyclohexane- 1,2-diacetals or the related butane-2,3-diacetals represents a new approach which has proved its value in complex oligosaccharide synthesis [124]. 

Dimethoxyethylidene, 349 a-Methoxybenzylidene, 349 l-(A,A-Dimethylamino)ethylidene Derivative, 349 (X-(A,A-Dimethylamino) benzylidene Derivative, 349 Butane-2,3-bisacetal, 350 Cyclohexane-1,2-diacetal, 351 Dispiroketals, 352... 

Hydroxy-3-phenyl- (zu 82% d.Th.) und 3-Methoxy-3-phenyl-propen (zu 84% d.Th.) liefem analog 3-Phenyl-propen, trans- und cis-1 -Phenyl-propen (in beiden Fallen im Verhaltnis 80 17 3). Benzyliden-cyclohexan und 1 -Benzyl-cyclohexen sind auf fol-gendera Wege zuganglich1 ... 

Y. Zang and G. B. Schuster, A Search for Photo Resolvable Mesogens Synthesis and Properties of a series of Liquid Crystalline, Axially Chiral l-Benzylidene-4-[4 (9p-alkylphenylOethnyl)phenyl] cyclohexanes, y. Org. Chem., 59(1994)1855. 

In 2010, the Sato group disclosed the synthesis of tetrodotoxin 86 starting from d-glucose, in which the Perrier carbocyclization of enol acetate 92 was employed for the construction of the cyclohexane core of tetrodotoxin. 4,6-O-Benzylidene derivative 99 was converted into pyranoside 93 possessing an exo-methylene group at C-3 (Scheme 12.47). m-CPBA oxidation of 93 stereoselectively provided epoxide 183. Alkaline hydrolysis of the epoxide in 183 followed by acetonide formation gave primary alcohol 184. Oxidation of 184 afforded aldehyde 185, which was converted into (Z)-enol acetate 92 by the action of acetic anhydride and potassium carbonate. When enol acetate 92 reacted with Hg(OAc)2, followed by NaCl treatment, the Perrier carbocyclization reaction successfully took place to afford a mixture of... 

Setzt man 4-substituierte Cyclohexanone 339 mit chiralen, optisch aktiven Yliden, z.B. 338, um, so erhait man die axial chiralen, optisch aktiven 4-substituierten Benzyliden-cyclohexane 340 i ). Die optische Ausbeute betragt 70—75%. 

Relatively soft, late transition-metal Lewis acids are also suitable catalysts for electrophilic fluorination. Indeed, the cationic chiral mthenium(II)-(15,25)-A,/V -bis(o-(diphenyl-phosphino)benzylidene)cyclohexane-1,2-diamine complex is a powerful catalyst for the enantioselective fluorination of (3-keto esters (Scheme 44.25). ... 

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