Indenes are important core structures in organic chemistry. Few simple arylallenes have been used to construct indene skeletons by Friedel-Crafts reaction. Lewis acid catalyzed reaction of ethenetricarboxylates 1 and arylallenes has been examined in this study. The reaction of arylallenes and ethenetricarboxylate triesters with SnCl(4) gave indene derivatives efficiently, via a conjugate addition/Friedel-Crafts cyclization reaction. On the other hand, the reactions of 1,1-diethyl 2-hydrogen ethenetricarboxylate and arylallenes or alkylallenes with SnCl(4) at -78 degrees C or room temperature and subsequent treatment with Et(3)N gave gamma-lactones. The reactions of triethyl ethenetricarboxylate and 1,1-dialkylallenes with SnCl(4) at room temperature also gave gamma-lactones.

The Lewis acid promoted reactions of 2‐substituted 2‐propenyl amides and the 2‐methylbuta‐2,3‐dienyl ester of ethenetricarboxylate have been examined. The reactions of 2‐substituted 2‐propenyl amides with AlCl3 gave 2‐oxo‐5,6‐dehydropiperidines as the major products. The reaction of 2‐methylbuta‐2,3‐dienyl ester with Lewis acids such as AlCl3 and SnCl4 gave 2‐oxo‐3,6‐dihydropyran as the major product. The preference for six‐ over five‐membered‐ring formation was observed.

Ethenetricarboxylic acid diester 1a is a useful compound bearing two reactive sites, a CO2H group and a Michael acceptor. Reactions of 1a and reagents with oxygen and nitrogen nucleophilic moieties have been examined. The reaction of 1a with 2-aminoalcohols in the presence of EDCI and HOBt in one pot gave N,O-containing heterocyclic compounds, regioselectively. The stepwise method has also been carried out. Deprotection of N-Boc protected aminoesters, followed by basic aqueous workup, gave various 1,4-oxazine derivatives. Deprotection of the O-TBS protected amides also leads to spontaneous cyclization and affords 1,4-oxazine derivatives. They have the opposite regiochemistry to those from the one-pot reaction. Thus, both ester or amide regioisomers can be prepared. These synthetic methods represent a new general strategy for the construction of diverse heterocyclic systems such as morpholine-derived heterocycles.

The Lewis acid promoted reaction of 1,1-diarylallenes with ketone derivatives was examined. The tin(IV) chloride promoted reaction of diarylallenes with vinyl ketones gave indene derivatives through a conjugate addition/cyclization reaction. The reaction of diphenylallene with diethyl oxomalonate in the presence of one equivalent of tin(IV) chloride at -40 °C gave diethyl hydroxy(3-phenyl-1H-inden-2-yl)malonate as the major product through a carbonyl addition/cyclization reaction, whereas the same reactants in the presence of 0.2 equivalents of tin(IV) chloride at 80°C gave diethyl (3-phenyl-1H-inden-2-yl)malonate. Diethyl hydroxy(3-phenyl-1H-inden-2-yl)malonate was also converted into the latter product on heating at 80 °C in the presence of 0.2 equivalents of tin(IV) chloride.