Table 1.

Method Development Study on Effects of NEt₃ and Molecular Sieves on Pyrrolidine-catalyzed Fulvene Formation Rates

Entry	R	R1	Method Aa: % 0.83 h (after completion)	Method Bb: % 0.83 h (after completion)
a	H	4-MeC6H4	47(98)	71(93)
b	H	4-MeOC6H4	70(97)	99(94)
c	H	4-Me2NC6H4	50(100)	67(97)
d	H	4-HOC6H4	9(85)	f
e	H	3-MeOC6H4	f	35(96)
f	H	3,4-(MeO)2C6H3	47(98)	79(99)
g	H	C6H5	23(96)	50(95)
h	H	4-ClC6H4	6(96)	18(96)
i	H	4-NO2C6H4	025	39c(30)h
j	H	3-NO2C6H4	0	45c(31)
k	Me	Me	69	86 (89)
l	Me	4-MeC6H4	0d	(82)e
m	Ph	Ph	0d	0
n	H	i-propyl	35	64(88)
o	R=R1= cyclobutyl		55	80(90)
p	R=R1=cyclopentyl		51	77(85)
t	Me	(CH2)2CO2H	74g
u	Me	(CH2)3CO2H	87g
w	H	2-BrC6H4		(50)
x	H	4-CF3C6H4		(45)

^aThe reactions completed within 24 h except entry d where the conversion was 88%;.

^bThe reactions completed within 5 h except in the case of 1h which was stirred overnight for completion.

^cThe reactions were performed in acetonitrile with 15 mol% pyrrolidine and 0.3 g/mmol molecular sieves and the data are for the 3^rd h.

^dAddition of 10 mol% of DBU did not result in fulvene formation after 24 h stirring at room temperature.

^eMethod B with 3 equiv of added pyrrolidine as catalyst; reaction time 48 h. The yield of the product when no MS was used is 79%.

^fReactions not performed; Method A: 5 mmol carbonyl compound, 2.5 equiv cyclopentadiene (CP), 1.5g 3A molecular sieves, 10 mol% pyrrolidine, 1.5 equiv. NEt₃, 5 mL MeOH; Method B: same as A, no NEt₃, 1.2 equiv CP.

^gMethod A without molecular sieves with 20 mol% of added pyrrolidine as catalyst; isolated yield after overnight stirring and regular aqueous work-up was performed (see Experimental Section).

^hThe reaction according to method B gave 10% fulvene. The main product cyclopenta-1,3-dien-1-yl(4-nitrophenyl)methanol and cyclopenta-1,4-dien-1-yl(4-nitrophenyl)methanol (1:1) was isolated in 40% yield after 18h stirring at room temperature.