Cycloproparenes: Approaches to cyclopropa[c]furan

Treatment of 6,6-dichloro-3-oxabicyclo[3.1.0]-hexane (7) with potassiumt-butoxide generates the ring-strained cyclopropene8 as a reactive intermediate. With 1,3-diphenylisobenzofuran compound8 is trapped as a 51 mixture of theexo- andendo-adducts11a and11b, respectively. With furan only the ring expanded vinylcarbene12 is intercepted and spirocycle13a is formed. Carbene12 is also captured by cyclohexene, 2,3-dihydrofuran, 2,5-dihydrofuran, and diphenylethyne to give22–25 respectively. A likely side product in these reactions is the pyran14.On leave from Petrolite Corporation, St. Louis, MO, USA.Taken in part from a lecture delivered at the International Chemical Congress of Pacific Basin Chemical Societies, Honolulu, December 1989 (Pacifichem '89); Abstract ORGN 016. A preliminary report was communicated (see ref. [13]).     

Synthesis of cyclopropa[c]indeno[1,2-b]quinolines through a MCR/Staudinger/aza-Wittig sequence

Spirocyclopropanes were prepared from aromatic aldehydes, 1,3-indandione and acetophenones through a halogenation/S_N2-displacement/Michael-initiated ring-closing sequence by a pyridinium-ylide-assisted multicomponent reaction, and their further use was also researched in the construction of cyclopropa[c]indeno[1,2-b]quinolines through subsequent Staudinger/aza-Wittig reactions.     

Syntheses of 1-substituted 4,4-dimethyl-1,2,3,4-tetrahydrobenzo[b]-1,4-azasilines and 1-substituted 3,3-dimethyl-1,2,3,4-tetrahydrobenzo[e]-1,3-azasilines

1-Substituted 4,4-dimethyl-1,2,3,4-tetrahydrobenzo[b]1,4-azasilines (X) and 1-substituted 3,3-dimethyl-1,2,3,4-tetrahydrobenzo[e]-1,3-azasilines (XIII) were synthesized by the intramolecular benzyne reaction of the corresponding N-substituted 2-(3-chlorophenyl)dimethylsilylethylamines (IX) and N-substituted (3-chlorobenzyl)dimethylsilylmethylamines (XII).     

Synthesis of novel 1,2,3,4-tetrahydrobenzo[c]-1,5-naphthyridines from pyrrolo[1,2-b]isoquinolines

1,2,3,4-Tetrahydrobenzo[c]-1,5-naphthyridine ( 5a ) was prepared by a novel synthetic route involving the rearrangement of (±)-(Z)-1,10a-dihydropyrrolo[1,2-b]isoquinoline-3,10(2H,5H)-dione oxime to afford 1,4-dihydrobenzo[c]-1,5-naphthyridin-2(3H)-one, which was reduced to 5a. The cholinomimetic activity observed with 5a prompted the synthesis and biological evaluation of additional analogues.     

Diphenylmethylidenecyclobuta[a]cyclopropa[d]benzene: synthesis and spectral characterization

[reaction: see text] The first derivative of the novel and highly strained rocketene (cyclobuta[a]cyclopropa[d]benzene) 5, namely, the C4 diphenyl-substituted exocyclic alkene 8, has been prepared in 16% overall yield as a yellow oil with properties fully consistent with its highly strained nature.     

Synthesis of 5-amino-1,2,3,4-tetrahydrobenzo[b][1,7]naphthyridines and 2,3,4,4a,5,6-hexahydrobenzo[c][2,6]naphthyridines

This paper describes the synthesis of some 5-amino-1,2,3,4-tetrahydrobenzo[b][1,7]naphthyridines and 2,3,4,4a,5,6-hexahydrobenzo[c][2,6] naphthyridines starting from anilines and 1-benzyl-4-ethoxycarbonylpiperidin-3-one. The compounds were prepared in order to study their potential acetylcholinesterase inhibitory activity.