Reaction of 2-Phenyl-2-(2,3,4-trimethoxyphenyl)ketene with Ethoxyethyne†

doi:10.7503/cjcu20140053

Abstract

Abstract:

Nieuwenhuis and Arens discovered the reaction of diarylketenes with alkynyl ethers leads to substituted azulenones in 1958. This reaction involved the construction of four C—C bonds in a single operation and provided facile access to a functionalized bicyclo[5.3.0]decane skeleton. Although the mechanism of this transformation was rationalized later by Woodward and Barton, respectively, the synthetic value of this reaction has not been demonstrated so far. In this work, 2-phenyl-2-(2,3,4-trimethoxyphenyl)ketene(9) as a new ketene was first synthesized from 1,2,3-trimethoxybenzene and ethyl 2-chloro-2-oxoacetate through 5 steps. The reaction of compound 9 with ethoxyethyne(2) produced two novel angular aryl-substituted azulenone products 11 and 12, whose isomeric structures were characterized by NMR and X-ray crystallographic analysis. Treatment of azulenone 11 with Lewis acid afforded azulenone 12. These results provided an additional experimental supported for a stepwise pathway rationalized by Woodward earlier on.

Key words: Azulenone, Diarylketene, Rearrangement, Norcaradiene(Ed.: P, H, N, K)

CLC Number:

O621.3

TrendMD:

WANG Zedong, YUE Xiaodong, CHEN Li. Reaction of 2-Phenyl-2-(2,3,4-trimethoxyphenyl)ketene with Ethoxyethyne^†[J]. Chem. J. Chinese Universities, 2014, 35(8): 1681.

Figures/Tables 6

Scheme 1 Formation of azulenone: Woodward and Barton mechanism

Scheme 2 Synthesis routes of 2-chloro-2-phenyl-2-(2,3,4-trimethoxyphenyl)acetyl chloride(8)

Scheme 3 Synthesis routes of methyl 2-phenyl-2-(2,3,4-trimethoxyphenyl)acetate(10)

Scheme 4 Synthesis routes of azulenones(11 and 12)

Scheme 5 Proposed formation mechanism of azulenone

Table 1 X-Ray crystallographic data of compounds 11 and 12

Compound	11	12
Empirical formula	C₂₁H₂₂O₅	C₂₁H₂₂O₅
Formula mass	354.39	354.39
Crystal system	Triclinic	Triclinic
Space group	P $1 ˉ$	P $1 ˉ$
a/nm	0.9420(3)	0.87035(11)
b/nm	1.1725(4)	1.02348(14)
c/nm	1.6971(5)	1.11669(18)
α/(°)	96.668(5)	66.61(3)
β/(°)	95.867(5)	80.03(4)
γ/(°)	101.572(5)	85.95(4)
V/nm³	1.8088(10)	0.8992(2)
Z	4	2
T/K	113(2)	113(2)
Wavelength/nm	0.071073	0.071073
Calculated density/(g·cm^-3)	1.301	1.309
Absorption coefficient/mm^-1	0.092	0.093
Absorption correction	Semi-empirical from equivalents	Semi-empirical from equivalents
F(000)	752	376
Theta range for data collection(°)	1.22—27.86	2.01—32.58
Max. and min. transmission	0.9890 and 0.98181	0.9889 and 0.9817
Refinement method	Full-matrix least-squares on F²	Full-matrix least-squares on F²
Data/restraints/parameters	8511/0/477	6465/0/239
θ ranges(h, k, l)	-12≤h≤12, -14≤k≤15, -22≤l≤22	-13≤h≤13, -15≤k≤15, -16≤l≤15
Reflections collected/unique	19142/8511 [R_int=0.0448]	14635/6465 [R_int=0.0442]
Completeness to θ=25.02°	98.5%	98.6%
Goodness-of-fit on F²	1.017	0.93
Final R indices[I>2σ(I)]	R₁=0.0457, wR₂=0.0915	R₁=0.0426, wR₂=0.1016
R indices(all data)	R₁=0.0734, wR₂=0.0998	R₁=0.0595, wR₂=0.1070

Table 1 X-Ray crystallographic data of compounds 11 and 12

Compound	11	12
Empirical formula	C₂₁H₂₂O₅	C₂₁H₂₂O₅
Formula mass	354.39	354.39
Crystal system	Triclinic	Triclinic
Space group	P $1 ˉ$	P $1 ˉ$
a/nm	0.9420(3)	0.87035(11)
b/nm	1.1725(4)	1.02348(14)
c/nm	1.6971(5)	1.11669(18)
α/(°)	96.668(5)	66.61(3)
β/(°)	95.867(5)	80.03(4)
γ/(°)	101.572(5)	85.95(4)
V/nm³	1.8088(10)	0.8992(2)
Z	4	2
T/K	113(2)	113(2)
Wavelength/nm	0.071073	0.071073
Calculated density/(g·cm^-3)	1.301	1.309
Absorption coefficient/mm^-1	0.092	0.093
Absorption correction	Semi-empirical from equivalents	Semi-empirical from equivalents
F(000)	752	376
Theta range for data collection(°)	1.22—27.86	2.01—32.58
Max. and min. transmission	0.9890 and 0.98181	0.9889 and 0.9817
Refinement method	Full-matrix least-squares on F²	Full-matrix least-squares on F²
Data/restraints/parameters	8511/0/477	6465/0/239
θ ranges(h, k, l)	-12≤h≤12, -14≤k≤15, -22≤l≤22	-13≤h≤13, -15≤k≤15, -16≤l≤15
Reflections collected/unique	19142/8511 [R_int=0.0448]	14635/6465 [R_int=0.0442]
Completeness to θ=25.02°	98.5%	98.6%
Goodness-of-fit on F²	1.017	0.93
Final R indices[I>2σ(I)]	R₁=0.0457, wR₂=0.0915	R₁=0.0426, wR₂=0.1016
R indices(all data)	R₁=0.0734, wR₂=0.0998	R₁=0.0595, wR₂=0.1070

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