Annelated oxetans are synthesized via thermal or pressure assisted cycloaddition of quadricyclane with the appropriate carbonyl bond activated by electron withdrawing groups; the new compounds are very stable and do not undergo the usual cycloreversion of four membered rings.

l-Chloro-2-(JV-chIoro-p-toluenesulfonamido)acenaphthene. To a well-stirred cold (0-2 °C) solution of 2.01 g of acenaphthylene in 15 mL of CH2C12 was added dropwise (10 min) a solution of 3.2 g of Cl2NTs in 15 mL of CH2C12. Workup as described above followed except that CC14 at -30 °C was used in place of ether at 0-2 °C to triturate the crude solid. The insoluble portion (0.9 g, mp 149-152 °C) was identified as 1chloro-2-p-toluenesulfonamidoacenaphthene (see below). The CC14 filtrate was evaporated and the residue was triturated with 15 mL of ether. Cooling to -30 °C (dry ice-acetone bath) gave a light-yellow solid, which was washed with two 3-mL portions of cold (-20 °C) ether to give 2.1 g (59.2%) of the N-chloro compound, mp 115-117 °C. The analytical sample had the following: mp 117-119 °C (ether); IR (CHC13) 1340, 1160 cm-1 (S02);

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~~ ~The reactions of difluoro-, dichloro-and dibromocarbene with quadricyclane (2) were examined. In all cases, conversions were low (4-15 %), but three distinct reaction courses were observed: cleavage, 1 ,taddition, and 1,4-addition. Difluorocarbene gave mainly 6-endo -(2,2-difluorovinyl)-cis-bicyclo[3.1 .O]hex-2-ene (8; 52-89 % relative yield), together with minor amounts of exo-3,3-difluorotricyclo[3.2.1.0Z~4]oct-6-ene (7; 13-17%), and 4,4-difluorotetracyclo[3.3.0.0z~8.03~6]octane (5; 2 4 % ) . Dichlorocarbene gave analogous products, but in relative yields of 35 (17), 51 (1 I), and 12% (16). The product 11 of 1,2-exo addition underwent further rearrangement to its allylic derivative 12. A small amount of 1,2-endo addition also occurred (2% of 14/15). Dibromocarbene gave predominantly products derived from rearrangement of the 1,2-exo (61 % of 20/21) and 1,2-endo adducts (loo/, of 23/24). In addition, a significant amount of 4,4-dibromotetracyclo[3.3.0.02~8.03~6]octane (25; 21 %) was formed. The cleavage product, 6-endo-(2,2-dibromovinyl)-cis-bicyclo[3.1 .O]hex-2-ene (26) was also observed (7 %). The yields and product compositions were compared to those obtained from norbornadiene (1) and found to be entirely different (Table I ) . for example no cleavage occurred with difluorocarbene.