29653
A synthetic method to prepare 2 , 4a - dihydro - 1H - fluorenes efficiently from gold ( I ) - catalyzed 1 , 2 - acyloxy migration / cyclopropenation / Nazarov cyclization of 1 , 6 - diyne carbonates and esters is described .
 2 , 4a - dihydro - 1H - fluorenes, gold ( I ), 1 , 2 - acyloxy, 1 , 6 - diyne carbonates and esters
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 2 , 4a - dihydro - 1H - fluorenes, gold ( I ), 1 , 2 - acyloxy, 1 , 6 - diyne carbonates and esters