8‐Bromobicyclo[5.1.0]oct‐1(8)‐cne (7), an intermediate for the preparation of 8‐substituted bicyclo[5.1.0]oct‐1(8)‐enes, was synthesized by denomination of 1,8,8‐tribromobicyclo[5.1.0]octane (6). Compound 7 underwent bromo‐lithium exchange followed by nucleophilic substitution reactions to generate bicyclo[5.1.0]oct‐1(8)‐ene (5), 8‐methylbicyclo[5.1.0]oct‐1(8)‐ene (10), and 8‐trimethylsilylbicyclo[5.1.0]oct‐1(8)‐ene (11). The bicyclic cyclopropenes 7, 5, 10, and 11 reacted with cyclopentadiene to form adducts 12, 13, 14, and 15, respectively. All of these Diels‐Alder adducts are endo‐exo isomers (endo‐addition from the view of the cyclopropene and exo‐addition from the view of the cyclooctene).
9‐Chlorobicyclo[6.1.0]non‐l(9)‐ene (4), a 2‐chlorinated 1,3‐fused cyclopropene, is synthesized and isolated from the dehalogenation of the l‐bromo‐9,9‐dichlorobicyclo[6.1.0]nonane, itself derived from cyclooctene. Compound 4 undergoes ring opening reaction to generate cyclooctenyl chlorocarbene (9) which reacts with water via conjugate addition and ipso‐addition to give (E)‐2‐(chloromethylene)cyclooctanol (7) and cyclooctene‐l‐carboxaldehyde (8), respectively. The conjugate addition of 9 with water is more favorable than the ipso‐addition by 3:1. Compound 4, which is stable at −25 °C for weeks without any decomposition, reacts with oxygen to produce 2‐chlorocyclonon‐2‐enone (12) via the ring‐opening reaction adduct, vinyl alkylcarbene 10.
After thiophene and furan were treated with n‐BuLi, respectively, the mixtures were reacted with various ketones and then dehydrated under acidic conditions. This reaction sequence led to the formation of 1‐(2‐heteroaryl)cycloalkenes and (2‐heteroaryl)alkenes. When the alkenes were treated with 10 mol % NIS, calix[4]arenes were produced as the major products, with minor amounts of calix[6]arenes sometimes being produced. Reducing the loading of NIS to 1 mol % and increasing its overall concentration to 6 M resulted in a substantial increase in the yield of hexaspirocyclohexyl calix[6]thiophene (from 2 to 66 %).
α,β‐Unsaturated N‐benzenesulfonyl imine 1 was treated with 1.1 eq methyllithium to afford 1,2‐addition adduct as a sole product. However, when compound 1 was treated with 2 eq MeLi, 1,2‐addition product, benzenesulfonamide derivative 3 and 2H‐1,2‐benzothiazine 1,1‐dioxide derivatives 4 and 5 were isolated.
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