Additions and Corrections - Orbital Interactions. 5. Through Space Effects of Substituents on the Reactivity of a Double Bond towards Diels-Alder and Epoxidation Reactions.

1980 ◽  
Vol 45 (26) ◽  
pp. 5433-5433
Author(s):  
M. Paddon-Row ◽  
H. Patney ◽  
R. Warrener
Keyword(s):  
Double Bond ◽  
Diels Alder ◽  
Orbital Interactions ◽  
Space Effects

scholarly journals Stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene: a general intramolecular Diels–Alder approach to tricyclic sesquiterpenes

1985 ◽  
Vol 63 (4) ◽  
pp. 993-995 ◽  
Author(s):  
Kazimierz Antczak ◽  
John F. Kingston ◽  
Alex G. Fallis
Keyword(s):  
Double Bond ◽  
Methyl Ester ◽  
Total Synthesis ◽  
Ring System ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
Total Syntheses ◽  
Methyl Group ◽  
Secondary Hydroxyl ◽  
Selective Hydrogenolysis

Stereoselective total synthesis of (±)-sinularene and (±)-5-epi-sinularene are described. The sequence employs a "blocked" cyclopentadiene in which the cyclopropane unit also serves as a latent methyl group. Thus intramolecular [4 + 2] cycloaddition of the substituted methyl spiro[2.4]hepta-4,6-dien-1-yl)-2-pentenoate 11 affords 5-benzyloxy-6-isopropyl-8-carbomethoxytetracyclo[5.4.01,7.02,4.02,9]undec-10-ene (12) which after selective hydrogenolysis generates the tricyclo[4.4.01,6.02,8]decane (sinularene) ring system. Removal of the secondary hydroxyl function (Ph3P/CCl4/CH3CN; H2/Pd/C), reduction of the methyl ester (LiAlH4), and introduction of the exocyclic double bond (acetate pyrolysis, 550 °C) completes the synthesis of (±)-sinularene in 14 steps from cyclopentadiene. A parallel series of reactions employing the isopropyl epimer of 12 affords (±)-5-epi-sinularene.

The Syntheses and Crystal-Structures of Decahydro-5,14:6,13:7,12-Trimethanopentacene and Decahydro-5,14-7,12-Dimethanopentacene: Two Useful Molecules for Investigating Laticyclic Hyperconjugation

1986 ◽  
Vol 39 (10) ◽  
pp. 1587 ◽  
Author(s):  
DC Craig ◽  
MN Paddonrow ◽  
HK Patney
Keyword(s):  
Crystal Structure ◽  
Ab Initio Calculations ◽  
Crystal Structures ◽  
Reductive Dechlorination ◽  
Photoelectron Spectrum ◽  
Alder Reaction ◽  
Diels Alder ◽  
Basis Set ◽  
Orbital Interactions ◽  
Diels Alder Reaction

The syntheses of decahydro-5,14:6,13:7,12-trimethanopentacene and decahydro-5,14:7,12-dimethanopentacene are described (see Schemes 1 and 2 respectively). Diels -Alder reaction of diene (10) with two equivalents of tetrachlorothiophen 1,1-dioxide (11) gave the adduct (12), which was aromatized to (13) through treatment with base. Reductive dechlorination (Na/ PriOH ) of (13) gave (6). A similar set of reactions performed on (17), itself prepared from cyclohexa-1,4-diene and two equivalents of hexachlorocyclopentadiene (15), gave (7). The crystal structures of (6) and (7) were determined. An interesting feature of the structure of (7) is the slight endo pyramidalization (by c. 3°) of the trigonal carbon atoms C 4a, C 7a, C 11a and C 14a. Model ab initio calculations (STO-3G basis set) on complexes (27) and (28), whose geometries were culled from the crystal structure of (6), indicate that significant laticyclic hyperconjugative interactions (c. 0.3 eV ) are mainly responsible for causing the observed splitting between the πs+πs and πs-πs levels in the photoelectron spectrum of (6). Orbital interactions through the pair of six connecting sigma bonds (OIT-6-B) in (6) have a negligible effect (c. 0.08 eV ) on these levels. In agreement with prediction, laticyclic hyperconjugation does not affect the πa+πa and πa-πa levels.

scholarly journals Zur Reaktivität des Germaethens Me2Ge=C(SiMe3)2: Mechanistische Aspekte der Diels-Aider- und En-Reaktionen [1] / On the Reactivity of Germaethene Me2Ge=C (SiMe3)2: Mechanistic Aspects of Diels Alder and Ene Reactions [1]

1996 ◽  
Vol 51 (6) ◽  
pp. 838-850 ◽  
Author(s):  
Nils Wiberg ◽  
Susanne Wagner
Keyword(s):  
Double Bond ◽  
Energy Difference ◽  
Diels Alder ◽  
Bond Polarity ◽  
Ene Reactions ◽  
Ene Reaction

Abstract Diels-Alder and ene reactions of germaethene Me2Ge=C(SiMe3)2 (2) with butadienes respectively, take place regioselectively, as well as stereoselectively. They are accelerated by an increasing tendency of substituents in butadiene or propene to donate electrons (e.g. 2-methylbutadiene > butadiene; 2-methylpropene > propene), and retarded by an increasing bulkyness of substituents in 1,4- or 1,3-positions (e.g. 1-methylbutadiene > 2-methylbutadiene; 1-vinylpropene > propene). It is concluded from these studies that Diels-Alder and ene reactions of 2 occur - like those of Me2Si=C(SiMe3)2 (1) or of ethenes >C=C< - in a concerted way and are HOMOdiene-LUMOdienophile and HOMOene-LUMOenophile controlled. Thus 2 and 1 behave as carbon analogues. With regard to a specific diene or ene (e.g. anthracene; toluene), 2 is the better dienophile or enophile than 1 or ethenes. With a fixed diene/ene mixture (e.g. butadiene/propene), 2 acts as the better dienophile, while 1 is the better enophile. These results can be explained by the π/π*- energy difference and the double bond polarity decreasing in the direction 1 > 2. Only cis-piperylene gives a [2+2] cycloadduct with 2. besides two [4+2] cycloadducts, and an ene reaction product

Exploratory synthetic investigations related to 12a-deoxypillaromycinone

2002 ◽  
Vol 80 (6) ◽  
pp. 728-738 ◽  
Author(s):  
Lan Wang ◽  
Sanath K Meegalla ◽  
Cheng-Lin Fang ◽  
Nicholas Taylor ◽  
Russell Rodrigo
Keyword(s):  
Double Bond ◽  
Catalytic Hydrogenation ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Step Procedure ◽  
Key Steps

Furfural is converted to suitably substituted AB synthon 21 for 12a-deoxypillaromycinone in 10 steps by a sequence involving the following key steps: intramolecular Diels-Alder reaction of a furan, 5-endo-trig cleavage of the oxabicyclo adducts 18, and catalytic hydrogenation of the double bond of a tetrasubstituted enone to produce 19. Enones 21a and 21b obtained by dehydrogenation of 19a and 19b, respectively, are then annulated with ethyl 2-methoxy-6-methylbenzoate in a four-step procedure to generate tetracyclic products 25 in 14 steps from furfural.

Unexpected Variations in the Reactivities and Selectivities of Acyclic and Cyclic Dehydrodipeptides in Diels-Alder Reactions

1998 ◽  
Vol 51 (11) ◽  
pp. 993 ◽  
Author(s):  
Brendan A. Burkett ◽  
Christina L. L. Chai ◽  
David C. R. Hockless
Keyword(s):  
Double Bond ◽  
Diels Alder

Author to whom correspondence should be addressed. The Diels-Alder reactions of some acyclic and cyclic dehydrodipeptides have been investigated. Our studies show that the reactivities of the dehydrodipeptides are sensitive to the environment of the double bond. In addition, theexo / endo selectivity of the cycloaddition is enhanced in the cyclic as compared to the acyclic systems.

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