2- Methyl-7-phenyl-2,4-heptadiene

Chlor-2-phenyl-ethyl)-methyl-E18, 1111 (En + R-S02-C1) Tricyclo 2.2.1]heptan 5-Chlor-3-methoxy-carbonyl- E17b, 1871 (Bicyclo[2.2.1 ]heptadien-PtCl2-Kompl. + H3C-OH/CO)... 

Similar to thermochemical intermolecular [2n- -2a] cycloadditions, the intramolecular version is also clearly promoted by phenyl substituents at the ends of the reacting cyclopropane bond. With phenyl groups in positions 2 and 4 of 3,3-dimethyltricyclo[3.2.0.0 " ]hept-6-ene (23, = Ph), a 60% yield of the 2n + 2a] cycloaddition product 24 (R = R = Ph) was obtained. If one of the phenyl groups is replaced by a methyl group (23, R = Me R = Ph), the yield decreased to 9%, even at 154°C. With two methyl groups in positions 2 and 4 (23, R = R = Me), only rearrangement products (bicyclo[3.2.0]heptadienes and cyclohepta-trienes) were observed. ... 

As indicated in the Introduction, the photochemistry of tropones proceeds via three different modes, called A, B, and C, with type C occurring in complex polycyclic troponoids. Mukai and Miyashi 72> have observed the first example of a photoreaction of a simple troponoid system to undergo the type C isomerization. Irradiation of 5-phenyltropolone methyl ether (104) in methanol yielded 3-methoxy-6-phenyl-A3>6-bicyclo-[3.2.0]heptadien-2-one (105). The effect of the substituent is important,... 

Zur Herstellung von 5-Methoxy-7-phenyl-2,6-heptadienal (88%) a us dem entsprechen-den Methyl-trimethylsilyl-acetal s.Lit.236. 

The unusual reversal of these 1,2-shifts can be observed where 35 is more stable. Thus, certain boronate complexes of the 7-borabicy-clo[2.2.1]heptadiene system will cleave, if certain steric factors permit (i7). Treatment of 1-halo- or l-methyl-2,3,4,5-tetraphenylborole with diphenylacetylene, reaction of the Diels-Alder adduct with excess methyllithium and heating leads, upon protolytic workup, to >80% yields of pentaphenylbenzene. Other labeling techniques showed that the phenyl group had migrated from carbon to boron (Scheme 3). 

Allylborane substrate. A = 4-methyl-l,6-heptadien-4-ol B = 4-phenyl-l,6-heptadien -4-ol C = 3,4,5-trimethyl-l,6- ... 

In contrast to furan, the exo-diastereoselectivity of the product oxetane in the photocycloaddition of spiro [4.2]-heptadiene 126 to benzaldehyde was reduced substantially to an exo/endo-r tio of 3.5 1 by the spiro-cyclopropane ring. The opposite exclusive endo-diastereoselectivity was found in the reaction with methyl ester of phenyl pymvate 127. Possibly emio-orientation of the large carbomethoxy... 

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