Two convenient new syntheses of ferrocenoyl chloride by triphosgene

Article abstract of DOI:10.1016/S0022-328X(00)00182-0

Two convenient new syntheses of ferrocenoyl chloride by triphosgene were reported. Firstly, ferrocenoyl chloride was conveniently prepared in 61.5% yield when triphosgene was reacted with ferrocene carboxylic acid in methylene dichloride at room temperature in the presence of triethylamine and DMAP. This new method for the synthesis of ferrocenoyl chloride enjoys a number of advantages in that the reaction is carried out under mild conditions and is cleaner without the formation of POCl₃, H₃PO₃ or SO₂ and dark-colored impurities. Secondly, ferrocene underwent reaction with one-third equivalent of triphosgene to give ferrocenoyl chloride in 38.1% yield. The main advantage of the second method for the synthesis of ferrocenoyl chloride is using cheap ferrocene as starting material.

Full text of DOI:10.1016/S0022-328X(00)00182-0

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Journal of Organometallic Chemistry 604 (2000) 287–289
Note
Two convenient new syntheses of ferrocenoyl chloride by
triphosgene
Wang Qingmin, Huang Runqiu *
Research Institute of Elemento-Organic Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai Uni6ersity,
Tianjin 300071, PR China
Received 20 December 1999; received in revised form 11 February 2000
Abstract
Two convenient new syntheses of ferrocenoyl chloride by triphosgene were reported. Firstly, ferrocenoyl chloride was
conveniently prepared in 61.5% yield when triphosgene was reacted with ferrocene carboxylic acid in methylene dichloride at room
temperature in the presence of triethylamine and DMAP. This new method for the synthesis of ferrocenoyl chloride enjoys a
number of advantages in that the reaction is carried out under mild conditions and is cleaner without the formation of POCl3,
H3PO3 or SO2 and dark-colored impurities. Secondly, ferrocene underwent reaction with one-third equivalent of triphosgene to
give ferrocenoyl chloride in 38.1% yield. The main advantage of the second method for the synthesis of ferrocenoyl chloride is
using cheap ferrocene as starting material. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Ferrocenoyl chloride; Triphosgene; Ferrocene; Ferrocene carboxylic acid
1. Introduction
Herein we report the two new syntheses of ferrocenoyl
chloride using triphosgene (bis(trichloromethyl)-
carbonate).
Ferrocenoyl chloride is an important synthetic inter-
mediate, and its derivatives exhibit antitumor [1a] and
insecticidal activities [1b]. For example, ferrocenoyl
acylhydrazines have excellent insecticidal activities
against insects of the orders Lepidoptera and
Coleoptera. Furthermore, ferrocenyl moiety is recently
incorporated into supramolecular arrays and sening
devices [2]. Ferrocenoyl chloride has been prepared by
the reaction of ferrocene carboxylic acid with a suitable
chlorinating agent such as phosphorus pentachloride
[3,4], phosphorus trichloride [5], and oxalyl chloride [6].
However, these procedures give dark-colored impurities
and provide low yields. Therefore, there exists a need
for new and mild synthetic method to the compound.
In a search for potentially biological active materials
containing the ferrocenyl moiety, the present methods
for the synthesis of ferrocenoyl chloride are developed.
2. Results and discussion
The syntheses of thiazolecarbonyl chlorides and m-
toluyl chloride by triphosgene in the presence or ab-
sence of DMF have been reported [7]. When this
method was applied to ferrocene carboxylic acid in
nitrogen atmosphere, no reaction could be observed.
We have found that ferrocenoyl chloride (3) was conve-
niently prepared in 61.5% yield when triphosgene (2)
was reacted with ferrocene carboxylic acid (1) in
methylene dichloride at room temperature (r.t.) in the
presence of triethylamine and DMAP (Scheme 1). The
triphosgene-mediated reaction for the synthesis of fer-
rocenoyl chloride outlined here enjoys a number of
advantages over the existing methods, in that the reac-
tion is carried out under mild conditions and is cleaner
without the formation of POCl3, H3PO3 or SO2 and
dark-colored impurities.
* Corresponding author. Tel.: +86-22-23502673; fax: +86-22-
23503438.
E-mail address: huangrq@nankai.edu.cn (H. Runqiu).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00182-0

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W. Qingmin, H. Runqiu / Journal of Organometallic Chemistry 604 (2000) 287–289
cheap ferrocene as the starting material. Moreover, the
experimental procedure is very simple.
The a carbon in the pyrrole ring can act as a nucleo-
phile with triphosgene and b-amino propionic esters or
nitriles to form intermediary pyrrole-2-carboxamides
[8]. Encouraged by the work, we developed the idea
that the carbon in ferrocene with high partial electron
density can also act as a nucleophile with triphosgene
to form a CꢀC bond. As shown in Scheme 2, ferrocene
(4) underwent reaction with one-third equivalent of
triphosgene (2) to give ferrocenoyl chloride (3) in 38.1%
yield. The solvents of choice in our hands have been
1,2-dichloroethane, methylene dichloride, or chloro-
form, but in principle, other solvents should be equally
useful. Other organic bases may substitute for triethy-
lamine in this reaction; however, we decided in favor of
triethylamine because of the ease of isolation of its
hydrochloride salt from organic solvents; triethylammo-
nium hydrochloride precipitates completely from most
organic solvents. When using more than a 1:3 molar
ratio of triphosgene to ferrocene only the ferrocenoyl
chloride (3) was obtained, and difunctional ferrocenyl
dicarboxychlorides were not observed. The difficulty of
introducing a second chlorocarbonyl group into the
ferrocene nucleus is interpreted in terms of deactivation
of the nucleus by the first chlorocarbonyl group intro-
duced. This route avoids the use of ferrocene carboxylic
acid, which has been prepared by multi-step process [9].
In conclusion, we developed the second efficient new
method for the synthesis ferrocenoyl chloride using
In the presence of anhydrous aluminium chloride, the
resulting ferrocenoyl chloride was reacted with fer-
rocene to give diferrocenyl ketone (5) in 50.6% yield
(Scheme 3).
3. Experimental
3.1. Instruments
All reactions were carried out under a nitrogen atmo-
sphere. Proton NMR spectra were obtained at 200
MHz using a Bruker AC-P 200 spectrometer. Chemical
shift values (l) are given in ppm. IR spectra were
recorded on a Shimadu-435 spectrometer. Elemental
analyses were determined on an MT-3 elemental ana-
lyzer. Melting points were taken on a Thomas–Hoover
melting-point apparatus and are uncorrected.
3.2. Synthesis
Triphosgene was prepared from dimethyl carbonate
and chlorine gas according to a reported procedure
[10], melted at 79°C. Ferrocene carboxylic acid was
prepared according to previous reports [9].
3.2.1. Ferrocenoyl chloride (3)
Method I. Under a nitrogen atmosphere, to the
stirred solution of triphosgene (0.89 g, 3.29 mmol) in
methylene dichloride (30 ml), was added dropwise a
solution of ferrocene carboxylic acid (0.72 g, 3.13
mmol), distilled triethylamine (3.29 mmol), and DMAP
(0.20 g, 1.65 mmol) in methylene dichloride (10 ml) at
0°C. Then the resulting mixture was stirred at 0°C for 1
h, followed by a further 11 h of stirring at r.t. The
solution was filtered and the filtrate was evaporated in
vacuo to dryness. Trituration with hot hexane precipi-
tated unreacted triphosgene; the mixture was filtered,
and the filtrate was concentrated under reduced pres-
sure, and the resulting residue was crystallized from
hexane to give a red crystalline solid (0.48 g, 61.5%),
m.p. 49–51°C (literature reference [4], m.p.=49°C);
1H-NMR (CDCl3): l 4.32 (s, 5H, C5H5), 4.63 (s, 2H,
C5H4), 4.91 (s, 2H, C5H4).
Scheme 1.
Scheme 2.
Method II. A solution of ferrocene (1.0 g, 5.4 mmol)
and distilled triethylamine (0.61 g, 6 mmol) in 1,2-
dichloroethane (15 ml) was stirred in an ice bath (nitro-
gen atmosphere). A solution of triphosgene (0.59 g, 2
mmol) in 1,2-dichloroethane (5 ml) was added drop-
wise. Then the resulting mixture was stirred in the ice
bath for 2 h, and subsequently stirred for a further 12
h at r.t. The solid was filtered and the filtrate was
evaporated in vacuo to dryness. The residue was tritu-
Scheme 3.

W. Qingmin, H. Runqiu / Journal of Organometallic Chemistry 604 (2000) 287–289
289
rated with hot hexane and filtered. The filtrate was
Acknowledgements
concentrated under reduced pressure, and the resulting
residue was crystallized from hexane to give a red
crystalline solid (0.51 g, 38.1%), m.p. 49–51°C (litera-
This work was supported by the National Natural
Science Foundation of China.
1
ture reference [4], m.p.=49°C); H-NMR (CDCl3): l
4.32 (s, 5H, C5H5), 4.63 (s, 2H, C5H4), 4.91 (s, 2H,
C5H4).
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