Photoreaction of (RS,SR)‐3‐Phenyl‐6‐hepten‐2‐ol. Benzene‐Olefin Cycloadditions as a Synthetic Route to [5.5.5.5] Fenestranes. Part III

Abstract

SummaryIrradiation of (RS,SR)-3-Phenyl-6-hepten-2-01 (3n) gave the photoproducts 6n-10n. Some reactions of 6n and 8n are reported. The regio-and diastereoselectivity observed in the photoreaction of substituted 5-phenylpentenes is discussed with respect to conformational preferences of the compounds to be irradiated.Introduction. -Polycyclic hydrocarbons in which four rings are annulated in such a way that they share a common C-atom are of interest for a study of the planarization of the tetracoordinate C-atom [l]. The [5.5.5.5]fenestranes ( = 'tetraquinacanes' or 'stauranes'; systematic name: tetracyclo[5.5.1 .04,13.0'",'3]tride~anes) are particularly attractive since they eventually might be transformed into a [12]annulene with a central C-atom [2]. Although a few syntheses of fenestranes have been reported [lc] [3], short and efficient routes for their preparation are still in need. We report our results of the intramolecular photocycloaddition of 3-phenyl-6-hept-en-2-01 (3n).

Diastereoselective Intramolecular meta Photocycloaddition of Side-Chain-Substituted 5-(2-Methoxyphenyl)pent-1-enes

“…[1] In particular, WenderЈs group has used the reaction for the synthesis of polyquinanes, [2] while Keese and co-workers have used it to prepare fenestranes. [3] The synthetic potential of the reaction is demonstrated by the photochemical behaviour of 5-phenylpent-1-ene and of 5-(2-methoxyphenyl)pent-1-ene (Scheme 1). Scheme 1.…”

Regioselective Photocycloaddition of Pyridine Derivatives to Electron-Rich Alkenes

“…Photochemical cycloaddition of benzene derivatives toward several types of alkenes has been extensively studied, and 2 + 2, 3 + 2, and 4 + 2 cycloadditions were reported. − The reaction has received much attention from both mechanistic and synthetic perspectives because it is also a useful method of synthesizing natural products. On the other hand, while the valence isomerization of azaaromatic compounds, such as pyridines, was reported three decades ago, − only a few reports for the photochemical cycloaddition with alkenes are known. − New developments in the ring transformation of heteroaromatics will result in useful synthetic methodology of heterocyclic compounds . Recently, we found that introduction of both electron-donating and -withdrawing substituents to the pyridine ring shows high reactivity toward dimerization and addition reaction. −

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