Indium- and gallium-mediated carbon-carbon bond-forming reactions in organic synthesis

Full text of DOI:10.1016/j.tet.2003.12.037

Tetrahedron 60 (2004) 1959–1982
Tetrahedron report number 671
Indium- and gallium-mediated carbon–carbon bond-forming
reactions in organic synthesis
*
Vijay Nair, Sindu Ros, C. N. Jayan and Bindu S. Pillai
Organic Chemistry Division, Regional Research Laboratory (CSIR), Trivandrum 695 019, India
Received 9 December 2003
Contents
1
2
.
.
Introduction
Indium
1959
1959
1960
1960
1960
1966
1967
1968
1968
1969
1971
1972
1972
1975
1977
1978
1978
1979
1979
1979
2
.1. Allylation reactions
2
.1.1. Allylation reactions of compounds with carbon–heteroatom multiple bonds
2
2
.1.1.1. With carbon–oxygen multiple bonds
.1.1.2. With carbon–nitrogen multiple bonds
2
2
.1.2. Allylation reactions of compounds with carbon–carbon multiple bonds
.1.3. Allylation reactions of compounds with other functional groups
2
2
2
2
2
.2. Palladium-catalysed reactions
.3. Propargylation reactions
.4. Reformatsky reactions
.5. Aldol reactions
.6. Miscellaneous reactions
3
4
.
.
Application to the synthesis of natural products
Gallium
4
.1. Allylation reactions
4
4
.1.1. Transmetallation of allylmagnesium bromide using gallium trichloride
.1.2. Transmetallation of allylindium sesquihalides using metallic gallium
4.2. Reformatsky reaction
Conclusions and future prospects
5
.
1. Introduction
2. Indium
Carbon–carbon bond formation constitutes one of the
fundamental processes in organic synthesis and a wide
variety of synthetic protocols have been developed to date
for effecting this, amongst which organometallic reactions
have played a major role since the discovery of Grignard
reagents at the turn of the last century. Over the years,
organometallic reagents have been developed utilising a
range of metals in the Periodic Table, indium and gallium
being the latest additions.
Even though indium, named for the luminous indigo line in
1
its spectrum, was discovered in 1863 by Reich, it has
emerged as one of the metals of interest in organic synthesis
only in the early 1990s. The low natural abundance of
indium may have been a deterrent in the explorations
involving this metal. Indium, however, enjoys a superior
position among other metals as far as its chemical behaviour
is concerned and this can be attributed to the following
properties:
(
(
1) indium metal is unaffected by air or oxygen at ambient
temperatures, this being a major advantage over most
of the other metals;
2) indium is practically unaffected by water, unlike other
metals such as Li, Na, etc;
(3) the first ionisation potential of indium (5.8 eV) is at a
Keywords: Organic synthesis; Indium; Galiium; Allylation; Reformatsky
reaction; Aldol reaction.
*
Corresponding author. Tel.: þ91-471-290406; fax: þ91-471-2491712;
e-mail address: vijaynair_2001@yahoo.com
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.12.037

1960
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
par with the alkali metals, for example, lithium or
sodium (,5 eV), are quite lower when compared to
zinc (9.4 eV), tin (7.3 eV) and magnesium (7.6 eV),
and indium is therefore an ideal candidate for SET
reactions;
In the late 1980s, Araki and co-workers introduced indium
5
metal for the first time in the Barbier reactions. Since then,
indium has been used to mediate a range of reactions which
are synthetically useful, amongst which, the carbon–carbon
bond-forming reaction occupies a pivotal position. Indium-
mediated carbon–carbon bond-forming reactions can be
broadly classified into the following categories:
(
(
4) indium exhibits low heterophilicity in organic reac-
tions, which makes it a suitable reagent for mediating
C–C bond-forming reactions where it can tolerate
oxygen and nitrogen functionalities and similarly,
indium reagents display low nucleophilicity, thus
permitting chemoselective transformations at groups
with similar reactivity;
5) most importantly, the element itself is without any
apparent toxicity, whereas organolead and organotin
reagents are highly and moderately toxic,
respectively.
(
(
(
(
(
(
1) Allylation reactions
2) Palladium-catalysed reactions
3) Propargylation reactions
4) Reformatsky reactions
5) Aldol reactions
6) Miscellaneous reactions
2.1. Allylation reactions
Cintas has reviewed the chemistry of organoindium
reagents in 1995, covering most of the literature available
Indium-mediated allylation reactions in highly polar
organic solvents such as THF or DMF proceed through an
2
up to that time. In 1999, Li and Chan have summarised the
reactions mediated by indium metal and indium compounds
6
indium sesquihalide, Allyl In X (1). Further treatment
3
2 3
3
a
in aqueous media. Since then, reviews dealing with
specific areas of indium-mediated reactions, although not
with KI or KBr enables the isolation of dialkylindium
halides. In reactions under aqueous conditions, the existence
of allylindium (2) as a transient, but discrete, intermediate
3
b,c
exhaustive, have appeared in the literature.
After the
7
completion of this account, we came across a fairly
comprehensive review on indium which covers the
was established by Chan and Yang (Fig. 1).
4
literature up to 2001; a few references in 2002 are also
2.1.1. Allylation reactions of compounds with carbon–
heteroatom multiple bonds
discussed in it. The focus of the present review is on
carbon–carbon bond formation mediated by indium, as well
as gallium, and the literature coverage is complete through
the first-half of 2003.
2.1.1.1. With carbon–oxygen multiple bonds. A variety
of ketones and aldehydes undergo indium-mediated allyla-
tion in DMF to afford the homoallylic alcohols in good
yields. Allylic iodides and bromides are equally reactive,
but the reactivity of allyl chloride is markedly diminished.
Even the less reactive allylic phosphates react with carbonyl
compounds in the presence of indium and indium iodide, but
ester and cyano groups are not susceptible to allylation
under these conditions. It is worthy to note that substrates
with active hydrogen such as ethyl acetoacetate and
salicylaldehyde can be allylated using indium in good
yields. With a,b-unsaturated aldehydes, the addition takes
Figure 1.
5
place in a 1,2-fashion (Scheme 1). Indium can also mediate
8
the allylation of aldehydes and ketones efficiently in water.
The indium-mediated allylation of aldehydes and ketones in
ionic liquids has no significant advantage over similar
9
reactions in conventional solvents. Enantioselectivity can
also be induced in indium-mediated reactions using external
1
0
chiral ligands.
Indium-mediated allylation of the steroidal aldehyde 9 in an
aqueous medium provides easy access to a wide variety of
Scheme 1.
Scheme 2.

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1961
2
tivity (Scheme 2).
2-hydroxysteroids with a moderate to high diastereoselec-
1
a trimethylsilyl group in high yields, the corresponding
reaction of 1,1,3-tribromo-3,3-difluoro-1-propene with
aldehydes afforded the coupling-reduction product, 24. It
is assumed that the reaction proceeds through a single
allylic indium intermediate and the negative charge in the
intermediate resides at the a-carbon (CF2 site). The
a-regioselectivity and the retention of the stereochemistry
of the double bond in these reactions were explained on the
1
Addition of methyl (E)-4-bromo-3-methoxycrotonate to
aldehydes in the presence of indium in an aqueous medium
delivers the b-hydroxyesters, the acidic hydrolysis of which
1
2
leads to Knoevenagel-type adducts (Scheme 3).
1
4
basis of this (Scheme 5).
The organoindium reagent derived from 5-bromo-1,3-
pentadiene and indium metal reacts with a variety of
aldehydes and ketones with excellent regioselectivity to
afford the non-conjugated diene products (g-pentadienyla-
tion) in respectable yields. In addition, the trienes derived
from the dehydration of condensation products provide a
rapid entry into complex multicyclic skeletons via tandem
1
5
[4þ2] cycloadditions (Scheme 6).
Araki and co-workers have shown that the reaction of 1,3-
dibromopropene with metallic indium in DMF or DMA
produced two types of organoindium species: g-bromoallyl-
indium and allylic diindium reagents. While the former gave
Scheme 3.
2-phenyl-3-vinyloxirane upon coupling with benzaldehyde,
Metallic indium adds to 3-bromopropenyl acetate or
benzoate either in THF or water, affording the correspond-
ing 3-acyloxyallyl organometallic compounds. This nucleo-
philic addition to aldehydes opens up a route to the alk-1-
ene-3,4-diols in good to excellent yields. The diastereo-
selectivity depends mainly upon the nature of the carbonyl
compound; conjugated aldehydes afford the syn adducts,
while unconjugated aldehydes display the opposite anti
the latter gave 1-phenylbut-3-en-1-ol. The indium-mediated
reaction of 1,3-dibromopropene with carbonyl compounds
in water, however, gave the bis-allylation products, with
both carbon–carbon bond formations occurring primarily
on the same carbon, which effectively constitutes a gem-
allyl dianion equivalent (Scheme 7). Aromatic aldehydes
generally exhibited a higher selectivity than their aliphatic
counterparts in product formation during the reaction.
Benzaldehyde and analogues bearing electron-withdrawing
groups gave mainly the gem-bis-allylation products. Inter-
estingly, with those analogues bearing electron-donating
groups, the formation of both gem- and 1,3-dialkylation
products was dramatically decreased and the selectivity was
1
6
1
3
stereopreference (Scheme 4).
Whereas the indium-mediated coupling of E-(3-bromo-3,3-
difluoro-1-propenyl)trimethylsilane with aldehydes gave
the corresponding gem-difluorohomoallyl alcohols bearing
Scheme 4.
Scheme 5.

1962
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
Scheme 6.
Scheme 7.
reversed compeletely to give the dienes and homoallylic
alcohols.
Indium-promoted allylation reactions of aldehydes using
-bromo-2-eno-pyranoside in aqueous media provided
4
the unsaturated analogues of C-branched sugars or
C-disaccharides, which can be elaborated to the branched
1
7
sugars (Scheme 8).
In general, allylation of an aldehyde with a g-substituted
allylic indium reagent occurs regioselectively at the
Scheme 8.

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1963
Scheme 12.
Indium-mediated allylation of difluoroacetyltrialkylsilanes
in aqueous media gives the homoallylic alcohols exclu-
sively. It is noteworthy that the common Brook rearrange-
ment, C- to O-silyl group migration, is totally suppressed in
these reactions, with no detectable formation of the enol
Scheme 9.
g-position to afford the g-homoallylic alcohol in the absence
of a sterically-bulky substituent at the carbonyl or allyl
bromide. Loh et al., however, have succeeded in synthe-
sising the a-homoallylic alcohol via indium-mediated
allylation without the use of a sterically-hindered sub-
stituent (Scheme 9). Interestingly, the solvent plays an
important role in determining the regioselectivity in these
reactions. While water (10 M) and water/dichloromethane
2
1
silyl ethers (Scheme 12).
Indium-mediated allylation of a-chloro carbonyl com-
pounds with various allyl bromides in aqueous media gave
the corresponding homoallylic chlorohydrins, which could
be transformed in to the corresponding epoxides in the
18
(10 M/10 M) exhibit excellent a-selectivity, DMF, ethanol,
THF and water (0.5 M) show exclusive g-selectivity.
2
2
presence of a base (Scheme 13). These reactions are
strongly dependent on both the substituents at the carbon
bearing the chlorine and the allyl bromide.
A one-pot asymmetric synthesis of a cyclic g-allyl-
substituted a-amino acid derivative was accompolished by
combining the proline-catalysed Mannich-type reactions of
aldehydes and N-PMP-protected a-imino-ethyl glyoxylate
by indium-promoted allylation in aqueous media (Scheme
With a,b-unsaturated ketones, allylindium sesquibromide
produced homoallylic indium alkoxide intermediates, which
can be induced to undergo a deoxygenative rearrangement
that results in vinylcyclopropane derivatives. The overall
reaction therefore involves a deoxygenative sequential
transfer of two allyl moieties from the indium sesquihalide
1
9
10). This is the first direct organocatalytic asymmetric
Mannich-type reaction in aqueous media.
2
3
species to the a,b-unsaturated ketone (Scheme 14).
The regioselectivity of the reactions of a,b-enones with
allylindium reagents in the presence of TMSCl has also
been studied. In the absence of TMSCl, 2-cyclohexen-1-one
reacted regioselectively with the allylindium reagent to
produce the 1,2-addition product, whereas only the 1,4-
addition product was obtained in the presence of TMSCl
2
4
(
Scheme 15).
Scheme 10.
A variety of organoindium reagents, generated in situ, have
been shown to react smoothly with 1,2-diones, resulting in a
high-yield synthesis of a-hydroxyketones. For example,
benzil, on treatment with indium and allyl bromide, in the
presence of sodium iodide in DMF at room temperature,
afforded 2-hydroxy-1,2-diphenyl-pent-4-en-1-one in 97%
yield (Scheme 16). In the absence of sodium iodide, the
reaction was very slow. It is noteworthy that no diallylation
occurred, despite the use of an excess of reagent.
Indole-3-carboxaldehydes, irrespective of the substituents at
N-1 and C-2, undergo indium-mediated reactions with allyl
bromide and indole to provide the symmetrical and
unsymmetrical bisindolylalkanes and with other hetero-
cyclic enamines, viz. pyrrole, pyrazole, 6-aminouracil and
imidazole, to provide the indolyl heterocyclic alkanes in
excellent yields (Scheme 11). In addition, substituents on
the allyl bromide do not affect these ternary reactions.
In each case, the allylation proceeds with complete
regioselectivity to provide only the g-addition product.
2
5
2
0
In related work, it was shown that an allylindium reagent
Scheme 11.

1964
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
Scheme 13.
Scheme 14.
2-Oxocarboxylic acids or their sodium salts undergo
indium-mediated allylation to provide the corresponding
2
7
2
-allyl derivatives (Scheme 18). These reactions afford
exclusively the g-addition product. In the reactions with
cinnamyl bromide or ethyl 4-bromocrotonate, a high
diastereoselectivity is observed.
Scheme 15.
Scheme 18.
Indium-mediated allylation of a-ketoimides derived from
Oppolzer’s sultam was accomplished in aqueous THF in
good yields and excellent diastereomeric excesses (Scheme
2
8
Scheme 16.
19). This method is very attractive for the preparation of
enantiopure a-hydroxyacids.
reacts chemoselectively with isatins to afford the oxindole
derivatives. In the case of substituted allylic bromides
such as cinnamyl and prenyl bromides, exclusive g-regio-
The reaction of quinones with allylindium reagents deserves
2
9
special mention (Scheme 20). The reaction of p-benzo-
quinone with allylindium sesquiiodide in DMF at 245 8C
2
6
selectivity was observed (Scheme 17).
Scheme 17.
Scheme 19.

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1965
Scheme 20.
Scheme 21.
gave the allylated product derived from 1,2-addition to the
carbonyl group. Treatment of the crude product with
silver(I) oxide in refluxing ether induced a [3,3]-sigmatropic
rearrangement to give the allylated p-benzoquinone 75 in
indium powder in DMF gives the corresponding gem-
diallylated derivatives in moderate to good yields (Scheme
3
3
24). This strategy offers a novel route to phthalides and
butenolides from cyclic anhydrides. With g-substituted allyl
halides, the reaction stopped at the monoallylation stage,
presumably due to steric hindrance, affording the hydroxy-
lactones. Unlike acid anhydrides, the behaviour of cyclic
imides towards allylindium reagents is rather complicated;
the outcome of the reaction depends on the structure of both
the imides and the indium reagents and the products are
9
1% overall yield.
The addition of allylindium species to b-ketophosphonates
proceeded to afford the corresponding b-hydroxyphospho-
nate, both the open-chain and the cyclic b-ketophospho-
3
0
nates reacting equally well (Scheme 21).
5
generally obtained in low yields.
Treatment of aryl phosphonates with allylindium reagents
in the presence of acetic acid afforded the corresponding
a-hydroxy alkylphosphonates in good yields under mild
conditions. This process works well with several different
allylic bromides and does not appear to be sensitive to steric
3
1
hindrance at the b-carbon (Scheme 22).
Scheme 22.
The allylation of acid chlorides with allyl, crotyl or prenyl
bromide and indium in DMF at room temperature provides a
mild and efficient method for the preparation of b,g-
3
2a
unsaturated ketones (Scheme 23). The indium-mediated
allylation of acyl cyanides with allyl halides in aqueous
media also affords the b,g-unsaturated ketones in moderate
Scheme 24.
The indium-mediated reaction of allyl bromide with
acylimidazoles or pyrazoles in aqueous media gives a
mixture of the tertiary alcohol and ketone (Scheme 25).
The reaction of simple alkyl and aryl acylimidazoles with
3
2b
to good yields.
3
4
Allylation of cyclic acid anhydrides with allyl halides and
Scheme 23.
Scheme 25.

1966
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
indium and allyl bromide gives predominantly the tertiary
alcohol, whereas the reaction of acylpyrazoles under
identical conditions results in the predominant formation
of the homoallylic ketone.
Indium-mediated intramolecular allylations of carbonyl
compounds have also been reported in the literature. Li
et al. have described a novel two-carbon ring expansion
through the indium-mediated Barbier-type reaction in water
3
5a
(
carbon ring expansion using indium.
Scheme 26).
They have additionally achieved a one-
3
5b
Scheme 29.
Oxime ethers derived from 2-pyridinecarboxaldehyde and
glyoxylic acid can be efficiently allylated in water with
3
9
allylic bromides promoted by indium (Scheme 30). When
the metal is positioned in the proximity of flanking
heteroatomic centers, chelation by indium is indeed
operative and affects both the reactivity and the stereo-
chemistry. Interestingly, the reaction of oxime ethers
derived from 3- and 4-pyridinecarboxaldehyde under
similar conditions was unsuccessful. When cinnamyl
bromide, crotyl bromide and ethyl bromocrotonate were
used, the indium-mediated allylation of oxime ethers
occurred with excellent regioselectivity, affording exclu-
sively the g-adduct. The reaction was found to be highly
stereoselective with cinnamyl bromide and ethyl bromo-
crotonate, whereas, with crotyl bromide, the stereo-
selectivity was diminished.
Scheme 26.
Indium-mediated intramolecular carbocyclisation in
aqueous media offers a stereoselective route to cis-fused
a-methylene-g-butyrolactones; the latter are structural
motifs present in many biologically-active natural products
3
6
(
Scheme 27).
Scheme 27.
2.1.1.2. With carbon–nitrogen multiple bonds. Aldi-
mines can be allylated in a simple Barbier-type reaction
using allyl bromide and indium powder in THF to afford the
3
7
homoallylic amines (Scheme 28).
Scheme 30.
Indium-mediated allylation of pyridinium salts with various
allylic halides affords the corresponding 2-substituted
Scheme 28.
1
,2-dihydropyridines with complete regioselectivity
4
0
(Scheme 31).
employed for the synthesis of the alkaloid (^)-dihydro-
This method has been successfully
Allylindium adds to a variety of tosyl and aryl hydrazones
derived from aromatic aldehydes and ketones at ambient
temperature in a DMF–H O solvent system to afford the
pinidine.
2
homoallylic tosyl hydrazides and homoallylic hydrazines,
The reaction of activated nitriles with allylindium in THF at
70 8C affords the corresponding allylation–enamination
products in high to excellent yields (Scheme 32). This
reaction provides a useful method for the synthesis of
3
8
respectively (Scheme 29). Various aldonitrones also
undergo allylation when treated with allylindium reagents
to yield the homoallylic hydroxylamines.
4
1

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1967
chemistry of the addition of the indium reagents is highly
regulated via chelation with the neighbouring hydroxyl
group.
Indium-mediated allylation of 1,1-dicyano-2-arylethenes in
aqueous media gave the Michael adducts in good yields
4
4
(
Scheme 35). Unfortunately, other electron-deficient
alkenes such as 1-cyano-1-ethoxycarbonylstyrene, diethyl
maleate and cinnamyl cyanide failed to react under these
reaction conditions.
Scheme 31.
Scheme 32.
highly-functionalised enamines, which are not easily
accessible by conventional methods.
Scheme 35.
2
.1.2. Allylation reactions of compounds with carbon–
The allylation of enamines with allyl bromide in the
presence of indium produces the tertiary homoallyl amines
carbon multiple bonds. The hydroxyl-bearing cyclo-
propenes undergo clean allylindation with allylindium
reagents in both organic and aqueous media, in which
chelation of the hydroxyl group to indium plays a central
role. The regio- and stereoselectivity have been regulated
both by the location of the hydroxyl group in the molecule
4
5
(Scheme 36). The reactivity of the enamines is mainly
1
influenced by the substitution (R ) on nitrogen. Pyrrolidine-
derived enamines are more reactive than those derived from
morpholine and dibenzylamine. The effect of substitution
2
3
(R and R ) on the olefinic carbon b to nitrogen was also
3
4
2
and the reaction solvents (Scheme 33).
studied. Enamines with only one aliphatic substituent R
2
(
R ¼H) are more reactive. With two aliphatic substituents
2
3
R and R , the reactivity is moderately decreased. On the
other hand, substitution (R ) by a phenyl group decreases
the reactivity considerably.
3
Scheme 36.
Scheme 33.
The reaction of allylic indium sesquihalides to allenols has
been found to proceed with high regio- and stereoselectivity
4
6
The allylindation of non-activated carbon–carbon double
bonds of norbornenols proceeds with high regio- and
stereoselectivity to afford the allylated products, together
with iodinated and oxygenated products (Scheme 34). The
product distribution can be controlled by changing the
reaction solvent. In these reactions, the regio- and stereo-
(Scheme 37). Unlike the substituents on the C-4 carbon,
substituents on the C-1 carbon of allenols significantly affect
the reaction. Secondary allenols show diminished reactivity
and the tertiary allenols do not react at all. In addition,
protection of the hydroxyl group of the allenol compeletely
inhibits the allylindation.
4
3
Scheme 34.

1968
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
bromides in aqueous media to provide the corresponding
homoallylic (and allenylic) or homopropargylic alcohols,
5
0
respectively, in moderate to good yields (Scheme 41). The
overall reaction can therefore be shown as a one-pot
deprotection-allylation/propargylation.
Scheme 37.
Carboindation of alkynols by allylic indium sesquihalides
proceeded in DMF at 100–140 8C via a syn addition
4
7
(
Scheme 38). Only the terminal alkynols underwent
allylindation. This is in sharp contrast to the known
carbometallations, in which addition to inner alkynes is
very common, whereas addition to terminal alkynes is rare.
Scheme 41.
Scheme 38.
The reaction of unactivated terminal alkynes with allyl
bromide and indium in THF at room temperature produces
the 1,4-dienes via regioselective addition (Scheme 39). In
the case of unprotected alkynols, the regioisomeric outcome
is found to depend upon the distance between the hydroxyl
group and alkyne moiety; propargylic substrates give linear
Indium-mediated allylation of 4-acetoxy-2-azetidinones
was accomplished by the treatment of indium and allyl
bromide in the presence of potassium iodide at room
temperature (Scheme 42). It is assumed that azetidinones
behaved as the imine equivalent in these reactions to
achieve the carbon–carbon bond formation at C-4 position.
4
8
5
1
1
,4-dienes, while the higher homologues afford exclusively
the branched 1,4-dienes and the protected compounds
always afford the corresponding allylated branched
1
,4-dienes.
Scheme 42.
Scheme 39.
2
.1.3. Allylation reactions of compounds with other
Allylindium, prepared from allyl bromide and indium metal
in THF, reacts with terminal epoxides at room temperature
to afford the corresponding bishomoallyl alcohols in excel-
functional groups. The 3-tert-butyldimethylsilyloxyalk-2-
enylsulfonium salts 129, derived from the reaction of
a,b-enones with dimethyl sulphide in the presence of
TBSOTf, undergo a novel nucleophilic substitution with
allylindium reagents to afford the silyl enol ethers of
g,1-unsaturated ketones 130, which correspond to the
5
2
lent yields and with good regioselectivity (Scheme 43).
Allylindium, prepared from allyl bromide and indium metal
in an aprotic solvent, reacts with terminal vinyl epoxides at
room temperature to afford various bishomoallyl alcohols in
moderate to high yields via a consecutive 1,2-shift reaction
4
9
Michael addition products, in good yields (Scheme 40).
Acetals and ketals undergo indium-mediated allylation and
propargylation reactions with various allyl or propargyl
5
3
and regioselective allylation (Scheme 44).
2.2. Palladium-catalysed reactions
With a variety of organic electrophiles such as aryl and
vinyl triflates, vinyl halides, dibromoolefins and alkynyl
iodides, allylindiums generated in situ underwent palla-
dium-catalysed allyl cross-coupling reactions (Scheme
5
4
45). The presence of various alkyl substituents at the
a-and g-positions did not diminish the efficiency and
selectivity of the allyl halides as coupling partners.
The palladium catalysed reactions of aldehydes with allylic
compounds such as allyl alcohol, trifluoroacetate, chloride,
Scheme 40.

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1969
Scheme 43.
Scheme 44.
Scheme 47.
Scheme 48.
Scheme 45.
carbonate, acetate or phenyl sulfone using the indium–
indium trichloride system in aqueous media afforded the
corresponding homoallylic alcohols. In the case of sub-
stituted allyl chloride, acetate and alcohol, the correspond-
ing branched homoallylic alcohols with exclusive anti
stereoselectivity were obtained. In these reactions,
indium(III) chloride plays a role in the formation of
p-allyl-palladium complexes from allylic compounds
and/or in the in situ-generation of the reactive indium(I)
The tandem palladium-catalysed and indium-mediated
arylative cyclisation of allenyl aldehydes and ketones to
form homoallylic cyclopentanols and cyclohexanols has
58a
been reported (Scheme 49).
A similar reaction was
observed with allenyl sulfonimines; in contrast to allenyl
58b
aldehydes, the trans isomer was not obtained in this case.
Grigg and co-workers have shown that the p-allylpalladium
species formed by a palladium-catalysed cyclisation of aryl
halides onto proximate alkynes, followed by allene inser-
tion, undergoes transmetallation with indium to afford an
allylindium species which then adds to aldehydes to yield
5
5
chloride by reaction with indium metal (Scheme 46).
5
9a
carbocyclic and heterocyclic dienes (Scheme 50).
In
another study, the same workers generated the p-allylpalla-
dium(II) complex by a palladium-catalysed cyclisation of
5
aryl halides onto proximate 1,3-dienes.
9b
Allenylindium intermediates generated by the reaction of
indium with propargyl bromides were employed as effective
partners in palladium-catalysed coupling reactions with a
variety of electrophiles to produce allenes, polyallenes and
unsymmetrical bis(allenes) in excellent yields with com-
plete regio- and chemoselectivity (Scheme 51). Surpris-
ingly, no propargylic cross-coupling product is formed in
any of these reactions.
Scheme 46.
Araki et al. have shown that the diindium reagent prepared
from 3-bromo-1-iodopropene successively coupled with
carbonyl compounds and then with aryl, alkenyl or allyl
halides in the presence of a Pd(0) catalyst to afford a
convenient one-pot synthesis of linear homoallylic alcohols
6
0
5
6
(
Scheme 47).
2.3. Propargylation reactions
Homoallylic alcohols were obtained in moderate to good
yields by the reaction of allylindium species generated by
the transmetallation of p-allylpalladium(II) complexes
arising from aryl iodides and allenes with aldehydes
Among the many metals employed for propargylation
reactions, indium has attracted special attention, due to its
mild reaction conditions, as well as its wide functional
group compatibility. Compared to the well-established
allylic indium chemistry, however, the synthetic potential
5
7a
(
conditions to afford the homoallylamines.
Scheme 48).
Imines also reacted under identical
7b
5

1970
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
Scheme 49.
Scheme 50.
Scheme 51.
Scheme 52.
of propargylic indium reagents has not yet been fully
exploited.
Indium-mediated homoallenylation of aldehydes with
4-bromo-3-[(trimethylsilyl)methyl]-1,2-butadiene in DMF
afforded 2-(2-hydroxyethyl) homoallenylsilanes in good
6
3
Indium-mediated coupling of aldehydes with prop-2-ynyl
bromides occurs regioselectively to give either homoprop-2-
ynylorallenylicalcoholsdependingontheg-substituentofthe
prop-2-ynyl bromides. With the parent prop-2-ynyl bromide,
the indium-mediated coupling with aliphatic or aryl aldehydes
affords mainly the homoprop-2-ynyl alcohols in good yields.
In contrast, when the prop-2-ynyl bromide isg-substituted, the
coupling products are predominantly or exclusively the
yields at room temperature (Scheme 54).
The regio- and diastereoselectivity of the indium-mediated
reaction of azetidinediones and propargyl bromide in
6
1
allenylic alcohols (Scheme 52).
Indium-mediated coupling of 1,4-dibromo-2-butyne with
carbonyl compounds in aqueous media proceeded regi-
oselectively to give good yields of the 1,3-butadien-2-
ylmethanols. 2,3-Dibutadienyldiindium tetrabromide,
formed by the reaction of 1,4-dibromobutyne with indium,
adds to different carbonyl compounds in the presence of
zinc fluoride to give almost exclusively the acetylenic diol
6
2
as a single diastereomer (Scheme 53).
Scheme 53.

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1971
Acyl cyanides also undergo indium-mediated propargyla-
tion or allenylation to give the corresponding propargylic or
allenic ketones in good yields. It may be noted that the
regiochemical preference in this case is the opposite of
that observed with aldehydes. With the parent pro-
pargyl bromide the indium-mediated coupling gives
exclusively the allenic ketones, whereas the g-substituted
propargyl bromides give exclusively the acetylenic ketones
6
5
Scheme 54.
(Scheme 56).
Scheme 55.
Scheme 56.
aqueous tetrahydrofuran at room temperature have also
been reported. In the event, the 3-substituted 3-hydroxy-b-
lactam moiety was obtained, but the observed regioselec-
tivity was very poor, with the allenic product slightly
predominating. Surprisingly, the regiochemical preference
was reversed in the indium promoted reaction by changing
the solvent system to a saturated aqueous solution of
ammonium chloride in THF, the expected alcohols being
obtained as a mixture of regioisomers, with the propargylic
Allenic alcohols undergo facile allenylation and propargyl-
ation in the presence of indium and indium tribromide
under ultrasonic irradiation to give E-2,5,6-heptatriene and
E-2-hepten-6-yne compounds in good regio- and stereo-
6
6
selectivity (Scheme 57).
2.4. Reformatsky reactions
The Reformatsky reaction, because of its selectivity and
wide applicability, is a valuable method for the synthesis of
6
4
alcohol preponderating (Scheme 55).
Scheme 57.

1972
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
hydroxyesters and their dehydration products. This reaction
involves the treatment of an a-bromoester with zinc in
the presence of an aldehyde or ketone to afford the
b-hydroxyester. Recently, several modified Reformatsky
reactions using other metals such as manganese, samarium,
etc. have been described.
synthetic organic chemistry, is often accomplished by the
aldol reaction. Indium can also promote such synthetically-
important aldol reactions. Indium metal as well as indium(I)
iodide are found to mediate the aldol condensation between
7
0
a-haloketones and aldehydes (Scheme 61).
2.6. Miscellaneous reactions
Indium is also found to effectively promote the Reformatsky
reaction of a-iodoesters with carbonyl compounds to
furnish the b-hydroxyesters. Although the methodology is
limited to the a-iodoesters, it is worthy of note that
no elimination products are formed during the process.
a,b-Unsaturated carbonyl compounds also undergo exclu-
sive 1,2-addition under modified Reformatsky reaction
A variety of useful synthetic transformations, besides those
described above, have also been accomplished via indium-
mediated reactions, illustrating the potential and versatility
of the organoindium species.
The indium-promoted pinacol coupling of aromatic carbo-
nyl compounds has been reported to take place in neutral
6
7
conditions (Scheme 58).
7
1
aqueous media under sonication conditions (Scheme 62).
In the absence of sonic waves, the reaction occurs much
more slowly and the yield of the diols is lower by a factor of
2
to 3-fold. The reaction of solid aldehydes with indium did
not take place in t-BuOH, and was very slow in water. The
reactions of aliphatic aldehydes and ketones with indium
were unsuccessful.
Recently, the In/InCl -mediated cross-coupling of methyl
3
vinyl ketone with benzaldehydes in aqueous media has been
7
2
reported (Scheme 63). In this reaction, the end product
was the b,g-unsaturated ketone and not the pinacol.
Scheme 58.
Butsugan et al. have applied the Reformatsky reaction to
p-quinones to give good yields of the b-quinol esters under
mild conditions and, using this methodology, the naturally-
occurring quinol ester jacaranone 190 was prepared
We have achieved a facile synthesis of unsymmetrical
pinacols by the reaction of aldehydes and chalcones in the
presence of indium/indium trichloride in aqueous media
(Scheme 64). This is the first report of a chalcone
participating in pinacol coupling reactions.
73
6
8
(
Scheme 59).
The indium-mediated 1,4-addition of an alkyl radical to
b-substituted conjugated alkenes in the presence of the
radical hydrogen source 1-ethylpiperidium hypophosphite
(
(
EPHP), the surfactant cetyltrimethylammonium bromide
0
CTAB) and the water-soluble radical initiator 4,4 -azo-
bis(4-cyanovaleric) acid (ABCVA) in aqueous media has
been developed. The reaction affords the 1,4-addition
products from various a,b-enones regiospecifically in high
Scheme 59.
7
4
Indium-mediated coupling of bromoacetonitrile and
-bromopropionitrile with a variety of aromatic acyl cyanides
afforded the corresponding aromatic a-cyanoketones in
yields (Scheme 65).
2
Using indium as a radical initiator, the intermolecular alkyl
radical addition to imine derivatives in aqueous media has
been achieved. The one-pot reaction based on radical
addition to glyoxylic hydrazone provides a convenient
method for preparing the a-amino acids. The indium-
mediated radical addition to an electron-deficient CvC
bond also proceeds effectively, to provide a new carbon–
carbon bond-forming method in aqueous media (Scheme
6
9
moderate to good yields (Scheme 60). Unlike benzaldehyde,
the reaction of acyl cyanides with bromoacetonitrile proceeds
successfullywithoutadditives. Itisnoteworthythatpractically
no reaction occurred in the absence of sonication.
7
5
66).
The indium-mediated atom-transfer cyclisations and reduc-
tive cyclisations depend upon the ratio of indium and iodine
7
6
used (Scheme 67). Treatment of an iodoalkyne with
indium (0.5 equiv.) and iodine (0.5 equiv.) in methanol
promotes the atom-transfer 5-exo cyclisation. In contrast,
the reaction with indium (2 equiv.) and iodine (1 equiv.)
gives rise to a reductive 5-exo cyclised product. Unfortu-
nately, these atom-transfer or reductive cyclisation reactions
are limited to iodoalkynes.
Scheme 60.
2
.5. Aldol reactions
Carbon–carbon bond formation via the selective reduction
of the carbon–halogen bond, an important operation in

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1973
Scheme 61.
Scheme 62.
Scheme 67.
Indium-catalysed aromatic Friedel–Crafts allylation in the
Scheme 63.
˚
presence of CaCO and 4 A molecular sieves results in the
formation of the corresponding allylated products in high
3
7
8
yields (Scheme 69). The high yields of the reaction in an
open vessel, using a catalytic amount of indium which is
re-usable after the work up without loss of activity, and the
simplicity of the reaction procedure offer advantages over the
existing allylation methods. The reactions occur regiospeci-
fically at the a-position of the allyl group and it is therefore
assumed that an allylic indium sesquihalide is not involved
and that the indium just acts as a Lewis acid catalyst.
Scheme 64.
Indium mediates a Barbier-type reaction between alkynyl
halides and aldehydes or ketones to give the secondary or
7
9
tertiary propargyl alcohols (Scheme 70). The highest
yields were obtained in dichloromethane at reflux, but a
mixture of the alcohol and ketone was obtained. It was
assumed that the ketone came from the Oppenauer oxidation
of the transient indium alkoxide, with the subsequent
reduction of benzaldehyde to benzyl alcohol. An increase in
the molar amount of benzaldehyde enhanced the Oppenauer
oxidation, whereas an excess of the phenylalkynyl iodide
prevented the oxidation.
Scheme 65.
A simple and general method for the synthesis of
tetrahydroquinoline derivatives via a novel domino reaction
of aromatic nitro compounds and cyclic enol ethers
(2,3-dihydrofurans) mediated and catalysed by indium in
water has been reported very recently (Scheme 68).
Indium can efficiently mediate the reaction between some
b-aminovinyl chlorodifluoromethyl ketones and a series of
77
Scheme 66.

1974
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
Scheme 68.
Scheme 72.
Scheme 69.
heteroaryl aldehydes, to afford the corresponding difluoro-
methylene compounds in good to high yields (Scheme
8
0
þ
2þ
7
1). It is assumed that indium species (In, In and/or In )
may act as an electron-transfer reagent to generate a reactive
difluorinated enolate. This mild approach seems to be
tolerant to a range of substituents and their position on the
aromatic ring; this is in sharp contrast to the electrochemical
approach, which was only successful with a substituent at
the para position of the aromatic ring.
Scheme 73.
Organoindium reagents derived from indium and diethyl
bromomalonates were added to a wide range of conjugated
enones in a 1,4-fashion in the presence of TMSCl under
mild conditions and the corresponding oxo-1,3-diesters
Cyclopropanation of electron-deficient alkenes can be
accomplished in DMF under mild conditions using
methylene dibromide in the presence of indium metal and
8
1
82
lithium(I) iodide (Scheme 72). Without the latter salt, the
yields are lower and no reaction takes place in ethereal
solvents. While electron-deficient alkenes give moderate to
good yields of the products, reactions with non-activated
and electron-rich alkenes such as cyclohexene and butyl
vinyl ether are unsuccessful. The Wideqvist-type synthesis
of cyclopropanes from carbonyl compounds can also be
were obtained in good to excellent yields (Scheme 73).
This protocol is an appealing alternative to the existing two-
step Michael reaction route that requires the generation of
the anion of diethyl malonate.
The a-chloro sulfides are used to control the stereoselec-
tivity in indium-promoted C–C couplings at room tem-
perature under aqueous and mixed aqueous/organic
8
1
achieved using indium.
Scheme 70.
Scheme 71.

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1975
conditions. The highest yields were obtained in water or in
8
3
50:50 mixtures of water and DMF (Scheme 74).
Reductive homocoupling of alkyl and aryl halides in the
presence of indium in DMF gives the dialkyls and biaryls in
8
4
good yields (Scheme 75).
Scheme 74.
The indium-mediated reductive coupling of aromatic acyl
cyanides affords the corresponding 1,2-diketones in mod-
erate to good yields under neutral and mild conditions
(Scheme 76). It is worthy of note that the reaction does not
require the exclusion of oxygen or anhydrous conditions as
8
5
required by SmI for effecting the same transformation.
2
Scheme 75.
The indium-mediated reaction of imines with ethyl
bromoacetate offers a simple synthesis of 3-unsubstituted
b-lactams (Scheme 77). Interestingly, the imines derived
from arylalkylamines, allylamine and p-anisidine produced
only the b-lactams, whereas the imines derived from aniline
produced b-aminoesters along with b-lactams.
8
6
Nitrones undergo deoxygenative reductive coupling and
subsequent cyclisation to the 3-arylamino-2,3-dihydroben-
zofuran derivatives in the presence of indium under aqueous
Scheme 76.
87
conditions at ambient temperature (Scheme 78).
3. Application to the synthesis of natural products
Indium-mediated reactions have found widespread appli-
cations in the synthesis of several natural products which are
biologically active. This aspect of indium chemistry is
briefly described here, with illustrative examples:
Scheme 77.
The d-lactone (þ)-boronolide 247, a pharmacologically-
active natural product, has been synthesised in an
enantiopure form with L-erythulose as the chiral starting
material. One of the key steps in this synthesis is the indium-
mediated diastereoselective aldehyde allylation (Scheme
8
8
79).
For the total synthesis of dysherbaine 251, a stereospecific
route to the key intermediate based on the indium-mediated
allylation reaction in aqueous media has been successfully
8
9
developed (Scheme 80). A remote phenyl substituent
group was used as a control element to achieve a high
stereoselectivity of the indium-mediated allylation of the
Scheme 78.
Scheme 79.

1976
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
Scheme 80.
Scheme 81.
Scheme 82.
ketone ester 248 to set the C-4 quaternary stereocentre in
9% de.
group constitutes one of the major steps in the total
synthesis of (þ)-goniofufurone 266, a cytotoxic agent
9
9
2
(
Scheme 83).
(^)-Methylenolactocin 257, an antitumour agent, was
prepared in five steps in which the indium-mediated
allylation reaction forms the key stage (Scheme 81).
Loh et al. have utilised the indium-mediated allylation of
aldehydes with a secondary allyl bromide in the presence of
La(OTf)3 in aqueous media for delivering a key inter-
mediate in the total synthesis of antillatoxin 271 (Scheme
84). In contrast to the reactions with primary allylic
bromides, the indium-mediated allylation of this secondary
allylic bromide afforded only the a-adduct.
9
0
In the synthesis of a six-carbon truncated sialic acid,
belonging to an important class of monosaccharides, the
indium-mediated allyl addition to a serine-derived aldehyde
9
3
9
1a
is utilised as a key step (Scheme 82).
synthesis of a seven-carbon truncated sialic acid using
indium has also been reported.
Recently, the
9
1b
The key step in the total synthesis of calystegine alkaloids
employs a zinc-mediated fragmentation of benzyl-protected
methyl 6-iodoglycosides, followed by the in situ formation
of the benzylimine and Barbier-type allylation with zinc,
The highly-diastereoselective indium-mediated allenyl-
ation of carbonyl compounds bearing an a-hydroxyl

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1977
Scheme 83.
Scheme 84.
Scheme 85.
magnesium or indium metal. The stereochemistry in the
pivotal allylation is controlled by the choice of the metal.
When the imine from the glucose- and galactose-derived
enal was reacted under Barbier conditions using mag-
nesium, a poor diastereoselectivity was observed, but, when
indium was used, the required R isomer was formed
exclusively. On the other hand, allylation of the imine
from the mannose-derived enal using indium gave only the
The chemical behaviour of gallium is similar to that of
aluminium. It is stable towards water, but it reacts
vigorously with halogens at low temperature. In contrast
to indium, it dissolves in aqueous alkali. It has a very low
melting point, but a rather high boiling point and shows the
longest liquid range of any element. This makes it a perfect
metal to be used in space-based engine controls, where the
temperature ranges are great. Gallium easily forms alloys
with most metals and has been used to create low-melting
alloys. Gallium is used as a doping material for semi-
conductors and has been used to produce solid-state items
such as transistors and light-emitting diodes.
9
4
S isomer (Scheme 85).
4. Gallium
Gallium metal was discovered spectroscopically by the
1
Compared to indium, gallium has not been extensively
explored from an organometallic perspective. It is only
recently that gallium has been used in allylation and
Reformatsky reactions.
French chemist de Boisbaudran in 1875. The name gallium
is coined from the Latin word ‘gallio’, the former name of
France.

1978
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
4
.1. Allylation reactions
The pioneering work by Araki et al. has shown the utility of
gallium metal in Barbier-type allylation reactions. The
gallium-mediated allylation of aldehydes and ketones with
allyl iodide under ultrasonication conditions afforded the
Scheme 88.
9
5a
homoallylic alcohols (Scheme 86). Aldehydes gave high
yields of the coupling products, whereas the reactivity of
ketones was somewhat lower. a,b-Unsaturated compounds
underwent exclusive 1,2-addition under these conditions.
Allyl bromide was found to be less reactive than allyl
iodide. Moreover, the reaction is highly chemoselective;
esters, cyanides and acyl chlorides cannot be allylated under
the conditions employed. Recently, gallium-mediated
1
-(a-Aminoalkyl)benzotriazoles react with allyl and pro-
pargyl bromides in the presence of gallium to give the
homoallylic and homopropargylic amines in high yields
9
8
(Scheme 89).
9
5b
allylation has also been reported in an aqueous medium.
Scheme 86.
Scheme 89.
Although the nature of the intermediate gallium species in
this reaction is not clear, the organogallium sesquiiodide can
be considered to be the most likely candidate by analogy
with the aluminium- and indium-mediated reactions.
Generally, these gallium-mediated Barbier-type allylation
reactions in THF require heating at reflux and other methods
for the generation of allylgallium species have therefore
been developed. These include:
In the presence of potassium iodide, lithium chloride and
gallium, aldehydes react with allylic bromides to afford the
(
(
i) transmetallation of allylmagnesium bromide using
gallium trichloride
ii) transmetallation of allylindium sesquihalides using
metallic gallium.
9
6
corresponding a- and g-adducts (Scheme 87). Interest-
ingly, the reaction shows a very high selectivity towards the
g-adducts. Under the same conditions, the reaction of
propargyl bromide with aldehyde exhibits a high acetylenic
selectivity.
4
.1.1. Transmetallation of allylmagnesium bromide
using gallium trichloride. The allylic gallium reagents
prepared from gallium trichloride and the corresponding
allylic Grignard reagent allylated carbonyl compounds in
excellent yields in an aqueous medium, as well as in organic
The gallium-mediated synthesis of a-hydroxy carbonyl
compounds in moderate to good yields has been accom-
plished by the use of the in situ-generated organogallium
reagents. For example, benzil, on treatment with allyl
bromide and gallium in presence of LiBr and KI in dry THF,
furnished 62% of the corresponding a-hydroxy carbonyl
99
solvents (Scheme 90).
Treatment of benzyl bromoacetate with the allylgallium
reagent, prepared from allylmagnesium chloride and
gallium trichloride in the presence of triethyl borane in
THF provided benzyl-4-pentenoate 289 in good yield
9
7
compound (Scheme 88).
1
00
(Scheme 91).
The addition of water as a co-solvent
improved the yields of the allylated product. This reaction
shows the stability of allylgallium species towards water.
Scheme 87.
Scheme 90.

V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
1979
Scheme 91.
4
.1.2. Transmetallation of allylindium sesquihalides
using metallic gallium. Allylgallium sesquibromide, pre-
pared by the reduction of allyl bromide with gallium metal
in the presence of a catalytic amount of indium, adds to
terminal alkynes in the presence of a tertiary amine to give
1
01
Scheme 94.
the 1,4-dienes (Scheme 92).
extent. The higher chemo-, regio- and stereoselectivities
shown by the allylindium reagents when compared to the
allyl Grignard reagents make them useful alternatives in
allylation reactions, especially in targeted syntheses. This
domain, however, offers opportunities for further explora-
tion with intriguing possibilities. Compared to indium, the
gallium-mediated reactions remain largely under-investi-
gated. It is likely that explorations in the area of gallium-
mediated reactions may uncover novel reactivity patterns.
Scheme 92.
Acknowledgements
The Grignard-type reaction of 1,4-diones with allylgallium
sesquibromide provides a facile and convenient method for
the allylation of quinones. Here, the allylgallium sesquiha-
lide is prepared by the reduction of allylic bromides with
gallium metal in the presence of a catalytic amount of
indium. p-Benzoquinone (72), for example, was treated with
the allylgallium reagent in the presence of sodium iodide in
THF to furnish the corresponding 2-allylhydroquinone
S.R., C.N.J. and B.S.P. thank CSIR, New Delhi for the
award of fellowships.
References and notes
1
. Bailar, J. C.; Emel e` us, H. J.; Nyholm, R. S.; Trotman-
Dickenson, A. F. Comprehensive inorganic chemistry;
Pergamon: New York, 1973; Vol. 1. p 1065.
1
02
(
291) in 67% yield (Scheme 93).
2
3
. Cintas, P. Synlett 1995, 1087.
. (a) Li, C. J. Tetrahedron 1999, 55, 11149. (b) Ranu, B. C.
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Gallium metal also mediates the Reformatsky reaction in a
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and a gallium redox system, carbonyl compounds react with
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1
03
(
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. Conclusions and future prospects
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1982
V. Nair et al. / Tetrahedron 60 (2004) 1959–1982
Biographical sketch
Vijay Nair has PhD degrees from the Banaras Hindu University (1967,
with Professor R. H. Sahasrabudhey) and the University of British
Columbia (1969, with Jim Kutney). Subsequently he was a postdoctoral
fellow with Josef Fried at the University of Chicago, Peter Yates in Toronto
and with Gilbert Stork at Columbia University. After a 16-year career
Sindu Ros was born in Irinjalakuda, Kerala State, India. She received her
BSc in Chemistry (St. Joseph’s College, Irinjalakuda) from the University
of Calicut and MSc from Pondicherry University. She received her PhD
(2003, University of Kerala) working under the supervision of Dr. Vijay
Nair at the Regional Research Laboratory (CSIR), Trivandrum. Currently,
she is a post-doctoral fellow in the research group of Professor David
S. Grierson at Institut Curie, Paris.
(Senior Research Chemist and Principal Scientist; outstanding scientist
award, 1981) with Lederle Laboratories (American Cyanamid Company) in
Pearl River, New York, he returned to his native Kerala State in India,
joined the Regional Research Laboratory (CSIR) in 1990 as its Deputy
Director, and established an Organic Synthesis Division there. During
1997–2001, he was the Director of the Institute. Presently, he is continuing
as a Director-Grade Scientist. In addition, he is an Honorary Professor in the
Department of Environmental Sciences, Cochin University of Science and
Technology. Dr. Nair’s research interests are in the areas of oxidative
electron transfer mediated C–C and C–Heteroatom bond forming
reactions, multicomponent reactions, heterocyclic synthesis via dipolar
cycloadditions, and medicinal chemistry. Dr. Nair has lectured in a number
of Universities in Germany in 1998 under the INSA-DFG exchange
fellowship. He has been an Invited Speaker at the 17th ICHC in Vienna in
1
999, MCR 2000, International Symposium in Munich, the 15th
International Conference on Organic Synthesis (ICOS) in Nagoya, Japan
in 2004. He was a Visiting Professor at the University of Pernambuco in
Brazil in May 2001. He is a Fellow of the Indian Academy of Sciences.
C. N. Jayan received his BSc and MSc from Mahatma Gandhi University
(Union Christian College), Kerala. He completed his PhD thesis under the
Bindu S. Pillai obtained her MSc in chemistry (first rank) from Mahatma
Gandhi University. She completed her PhD thesis (2003) under the
supervision of Dr. Vijay Nair, at the Regional Research Laboratory (CSIR).
Subsequently, she joined the group of Professor Robert Coates at the
University of Illinois in Urbana-Champaign, as a post-doctoral fellow.
guidance of Dr. Vijay Nair at the Regional Research Laboratory (CSIR) and
obtained the degree in 2001 from the Cochin University of Science and
Technology. During 2001–2002, he was a post-doctoral fellow with
Professor Alfred Hassner at Bar-Ilan University, Israel. Currently, Jayan is
working as a Visiting Fellow with Dr. Kenneth L. Krik at NIDDK of
National Institute of Health, USA.