3 Ο© 2] Co-cyclization / Nickel(0) catalysis / Palladium(0) catalysis / 4-Methylenespiro [2.4]
heptane derivatives
Bicyclopropylidene (1) readily undergoes a palladium(0)-ca-ates 2aΟͺ5 with the electron deficient alkenes and the cycloadducts 6 and 7 with the strained alkenes in acceptable to talyzed [3 + 2] co-cyclization with electron deficient alkenes (methyl acrylate, methyl trans-crotonate, methyl cinnamate good yields (56 to 83%). In contrast to palladium(0) catalysts nickel(0) complexes catalyze both distal ring opening of 1 and diethyl fumarate) as well as with some strained alkenes (norbornene, norbornadiene) by distal ring cleavage of one and oxidative coupling of the two double bonds when 1 is reacted with e.g. diethyl fumarate. The result is a mixture of the three-membered rings of 1. All these co-cyclizations are regioselective with respect to 1 as well as regio-and ste-of the methylenecyclopentane derivative 5 with the [2 + 2] cycloadduct 8 and the cotrimer 9. reoselective with respect to the alkenes to give the corresponding 4-methylenespiro [2.4]heptane-trans-6-carboxyl-FULL PAPER 2]. Οͺ MS (EI); m/z (%): 166 (8) [M Ο© ], 135 (9) [M Ο© Οͺ OCH 3 ], 107 dium(I) catalysts are able to either induce isomerization of (100) [M Ο© Οͺ CO 2 CH 3 ], 91 (91), 79 (56), 77 (23). Οͺ MS (HR-EI): 5 to the ethenylcyclopentene derivative 11 or in the presence 166.0993 (C 10 H 14 O 2 : calcd. 166.0994). Οͺ C 10 H 14 O 2 (166.2): calcd.
of an alkyne as e.g. 2-butyne to catalyze a [5 Ο© 2] cycload-