Ring olefins

Attempts to extend this reaction to the five-membered ring olefins 1-methylcyclopentene and norbomene resulted in 1-methylcyclopentane and methylenecyclopentane for the former and products (43)-(48) for the latter(80) ... 

The selective reduction of the D-ring olefin in 106 using a partially poisoned catalyst (Pd/C, 0.25 % pyridine) provided intermediate 107 (83 %), which was epimerized at -78 °C with sodium methoxide (HOAc quench at -78 °C, 89 %) (Scheme 10.9). Deoxygenation by means of tosyl hydrazone 108 and subsequent treatment with catechol borane and tetrabutylammonium acetate gave pentacyclic... 

Dicyclopentadiene has produced some interesting results. With rhodium catalyst at 115°C in tetrahydrofuran (THF), the dialdehyde was produced in good yield at 180°C that reaction proceeds further to form the diol in 67% yield (67). With a rhodium catalyst modified by excess triphenyl phosphite, the unsaturated monoaldehyde was obtained in a rapid reaction under very mild conditions (68, 69). The nonstrained 5-membered ring olefin required more strenuous conditions for hydroformylation. Either compound could be obtained in good yield by proper choice of conditions. 

The BINAL-H reagents exhibit exceptionally high enantioface-dif-ferentiating ability in the reduction of prochiral ketones that have unsaturated substituents such as aromatic rings, olefinic and acetylenic groups, etc. The general sense of asymmetric induction of simple car-... 

A. Adding H to the ring olefinic carbon and Cl to the nonring olefinic carbon ... 

Adding Cl lo (he ring olcfinic carbon and 11 to the non ring olefinic carljon ... 

The study of chiral 1,4-threitol-derived dioxolanes was also extended to a series of medium and large ring olefins. Very high diastereoselectivities were obtained for both (Z)- and ( -configurated olefins in ring sizes of five to sixteen63. 

The well-established linear relationship between and n bond order in 6-membered ring olefinic and aromatic compounds has been shown to exist in the 5-membered ring series, as exemplified by a series of cyclopentadienyl ylids. ... 

Treatment of d-trans-limonene with an acid catalyst leads to isomerisation of the terminal bond into the position between the isopropyl residue and the ring. By doing this, the system gains free energy by generating a tetrasubstituted double bond and one which is in conjugation with the ring olefin. Further isomerisation would be... 

Table 2.57 Ring Olefin Cross-Metathesis —cont d...

Strained small ring olefins are also highly suitable for ROM/enyne RCM reactions. An extended domino ROM/enyne RCM/diene RCM process leading to a... 

Photochemical cycloaddition of cis-cyclo-octene to benzene gives a mixture of the 1,2-adduct (211) and the exo- and endo-1,3-adducts (212). A study of the photochemical cycloaddition of olefins, including medium-ring olefins, to benzene and substituted benzenes, shows that the 1,2-photocycloaddition differs from the 1,3-process in requiring an olefin of either donor or acceptor character the donors add endo, the acceptors add exo. ... 

Five-membered Rings Olefin Synthesis Acyclic Diastereoselection... 

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