Intramolecular Butenolide Allene Photocycloadditions and Ensuing Retro-Ene Reactions of Some Photoadducts

This report describes intramolecular [2+2] photocycloadditions of several butenolides with an allenylmethyl substituent at the 5‐position. These photosubstrates were prepared from 2‐(silyloxy)furans through silver‐mediated reactions with allenylmethyl bromides. Two cases were studied where the lacto...

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Published in:	European Journal of Organic Chemistry Vol. 2011; no. 17; pp. 3146 - 3155
Main Authors:	Lutteke, Ginger, Kleinnijenhuis, Roel A., Jacobs, Ivo, Wrigstedt, Pauli J., Correia, Ana C. A., Nieuwenhuizen, Rowan, Buu Hue, B. T., Goubitz, Kees, Peschar, René, van Maarseveen, Jan H., Hiemstra, Henk
Format:	Book Review Journal Article
Language:	English
Published:	Weinheim WILEY-VCH Verlag 01-06-2011 WILEY‐VCH Verlag Wiley-VCH
Subjects:	Alicyclic compounds, terpenoids, prostaglandins, steroids Chemistry Cycloaddition Cyclobutane Exact sciences and technology General and physical chemistry Heterocyclic compounds Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives Heterocyclic compounds with only one n hetero atom and condensed derivatives Organic chemistry Photochemistry Physical chemistry of induced reactions (with radiations, particles and ultrasonics) Preparations and properties Retro-ene reaction Silver-mediated allylation Small ring systems Solanoeclepin A Terpenoids Nitrogen heterocycle Furan derivatives Lactam Organic siloxane Photochemical reaction Oxygen heterocycle Ring cleavage Allylation Unsaturated compound Bicyclic compound Hexane Chemical synthesis Nematoda Photochemistry Intramolecular reaction Terpenoid Silver-mediated allylation Four membered ring Carbon-hydrogen bond Chemical bond Solanoeclepin A Reverse reaction Lactone Transition metal Organic bromine compounds Retro-ene reaction Silver Cycloaddition Ultraviolet radiation Small ring systems Ene reaction Cyclobutane derivatives Acetonitrile Helmintha Irradiation Nemathelminthia Cyclobutane Invertebrata Allenic compound Ethylenic compound Acetone
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Summary:	This report describes intramolecular [2+2] photocycloadditions of several butenolides with an allenylmethyl substituent at the 5‐position. These photosubstrates were prepared from 2‐(silyloxy)furans through silver‐mediated reactions with allenylmethyl bromides. Two cases were studied where the lactone was replaced by an N‐Boc‐lactam. Irradiations of the photosubstrates were carried out with 300 nm UV‐light in acetonitrile/acetone mixtures. Crossed cycloadducts were produced in good yields via cycloaddition of the heterocyclic double bond with the allene internal double bond. The products were γ‐lactones (γ‐lactams) containing the strained 5‐methylenebicyclo[2.1.1]hexane skeleton. In some cases the products were unstable due to remarkably facile retro‐ene reactions (1,5‐hydrogen shifts) leading to unique α,β‐unsaturated γ‐lactone derivatives. These reactions occurred only with well‐oriented C–H bonds so that strain‐releasing four‐membered ring opening could take place. This retro‐ene reaction was studied in detail for more highly substituted derivatives in order to establish its relevance in connection with the instability of the natural terpenoid solanoeclepin A, the hatching agent of potato cyst nematodes. To this end, the methylenecyclobutane moiety in one of the cycloadducts was converted into a bicyclo[2.1.1]hexan‐5‐one (cyclobutanone) substructure. Intramolecular photocycloadditions of butenolides with a 2,3‐butadienyl substituent at the 5‐position led to tricyclic molecules with a methylenecyclobutane moiety as the core unit, resulting from regioselective crossed [2+2] cycloaddition of the internal allene C=C bond. The products from butenolides with an alkyl substituent at the 3‐position were susceptible to rearrangement by a thermal retro‐ene processproviding ‐methylene‐‐lactones. The structure of two key products was proven by X‐ray crystallography. The relevance of the retro‐ene process was investigated in connection with the known thermal instability of solanoeclepin A, the natural hatching agent of potato cyst nematodes. In this respect one of the photocycloadducts was converted into a cyclobutanone.
Bibliography:	ArticleID:EJOC201100245 istex:C6B1CB4D5DF5126534E113B4792D71C26DBE2CC9 ark:/67375/WNG-0B4CTDG5-T
ISSN:	1434-193X 1099-0690
DOI:	10.1002/ejoc.201100245