1. L-Proline Catalysed Domino Reactions for the Synthesis of Heterocycles
Author(s): Sethuraman Indumathi, Jose C. Menendez and Subbu Perumal
Affiliation: Department of Organic Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai 625021, India.
L-Proline is a cheap, water-soluble organocatalyst that is able to induce the synthesis of a large number of heterocyclic systems. This work is reviewed, with emphasis on the literature of the 2005-2011 period. The domino reactions have been classified according to the nature of the first step of their proposed mechanisms, as follows: (i) iminium-initiated domino mechanisms; (ii) enamineinitiated domino mechanisms; (iii) reactions proceeding via the intermediacy of dienamines; (iv) reactions in which proline acts as a Lewis base and (v) L-proline/metal catalysed reactions.
2. Multicomponent 1,3-Dipolar Cycloaddition Reactions in the Construction of Hybrid Spiroheterocycles
Author(s): Natarajan Arumugam, Raju Suresh Kumar, Abdulrahman I. Almansour and Subbu Perumal
Affiliation: Department of Chemistry, College of Science, King Saud University, PO Box 2455, Riyadh, Saudi Arabia; and Department of Organic Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai 625 021, Tamilnadu, India.
Spiroheterocyclic ring systems are attractive synthetic targets due to their interesting conformational features and their structural implications on their activity in biological systems. Consequently, a vast deal of research by synthetic organic as well as medicinal chemists pertains to the synthesis of these heterocycles employing diverse synthetic methodologies. Among them, one-pot multicomponent 1,3-cycloaddition reactions have emerged as preferred synthetic protocol in view of their convergence, atom economy, ecofriendliness, flexibility and facile automation. This review article focuses on the assembly of mono-, di- and multispiro heterocyclic hybrids via aforesaid synthetic methodologies with a variety of dipolarophiles.
3. Microwave Assisted Organic Synthesis: Cross Coupling and Multicomponent Reactions
Author(s): Amit Kumar Gupta, Neetu Singh and Krishna Nand Singh
Affiliation: Department of Chemistry, Centre of Advanced Study, Banaras Hindu University, Varanasi-221005, India.
Impact of microwave radiation on organic chemistry has been assessed by workers time to time. This review covers selected recent examples form cross-coupling reactions, multicomponent reactions along with some cycloaddition reactions to reveal the impact of microwave on organic synthesis.
4. Applications of Ultrasound in Organic Synthesis – A Green Approach
Author(s): Saurabh Puri, Balbir Kaur, Anupama Parmar and Harish Kumar
Affiliation: Department of Chemistry, Sant Longowal Institute of Engineering & Technology, Longowal-148106 (Pb.), India.
Ultrasound irradiation differs from conventional energy sources (such as heat, light, or ionizing radiation) in time, pressure, and energy per molecule. The use of ultrasound waves in organic synthesis has attracted an increasing interest over the last years. Use of ultrasound waves as alternative source of energy is of great interest in the area of green and pharmaceutical chemistry. This review will focus on the uses of ultrasound waves in heterocyclic chemistry, condensation reactions, substitution reactions, oxidation, reduction, addition reactions, photochemical reactions, protection/deprotection reactions, coupling reaction photochemical reactions, polymerization reactions etc
5. Renewable Energy via Photocatalysis
Author(s): Ravikrishnan Vinu and Giridhar Madras
Affiliation: Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India
The generation of renewable energy through photocatalysis is an attractive option to utilize the abundantly available solar radiation for a sustainable future. Photocatalysis refers to charge-carrier, i.e. electron and hole, mediated reactions occurring on a semiconductor surface in presence of ultraviolet or visible light radiation. Photocatalysis is a well established advanced oxidation technique for the decontamination of toxic organic pollutants to CO2 and H2O. However, the generation of energy in the form of hydrogen, hydrocarbon fuels and electricity via photocatalysis is an upcoming field with great many technical challenges towards practical implementation. This review will describe the fundamental reaction mechanism of (i) photocatalytic water splitting, (ii) photocatalytic H2 generation in presence of different sacrificial agents, (iii) H2 and electricity generation in a photofuel cell, (iv) photocatalytic reduction of CO2 to hydrocarbons and useful chemicals, and (v) photocatalytic water-gas shift reaction. A historic and recent perspective of the above conversion techniques, especially with regard to the development of TiO2-based and non-TiO2 materials is provided. The activity of different materials for the above reactions based on quantifiers like reaction rate, quantum yield and incident-photon-to-current efficiency is compared, and key design considerations of the “best” photocatalyst or photoelectrode is outlined. An overall assessment of the research area indicates that the presently achieved quantum efficiencies for the above reactions are rather moderate in the visible region, and the goal is to develop a catalyst that absorbs visible radiation, provides good charge-carrier separation, and exhibits high stability for long periods of usage.
6. Non-Metathetic Behaviour of Olefin Metathesis Catalysts
Author(s): Sambasivarao Kotha, Shilpi Misra, Gaddamedi Sreevani and Bandarugattu V. Babu
Affiliation: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.
We describe various non-matathetic reactions catalyzed by metathesis catalysts. These examples include: isomerization of olefins, dehydrogenative oxidation, dihydroxylation, allylic alcohol to methyl ketone conversion, dimerization, vinylation of acetylenes, hydrosilylation, Kharasch addition, cyclopropanation, cycloisomerization, hydrogenation, deprotection of N- or O-allyl groups, [2+2+2] cyclotrimerization, [3+2] and [4+2] cycloaddition reactions. These advances indicate that metathesis catalysts have potential to generate new strategies other than the metathesis based methodologies.
7. Pyrrole: Chemical Synthesis, Microwave Assisted Synthesis, Reactions and Applications: A Review
Author(s): Shrinivas D. Joshi, Uttam A. More, Venkatrao H. Kulkarni and Tejraj M. Aminabhavi
Affiliation: Department of Pharmaceutical Chemistry, S. E. T’s College of Pharmacy, S. R. Nagar, Dharwad 580 002, Karnataka, India.
Pyrrole is one of the main five membered heterocyclic systems reported for its various chemotherapeutic activities. Subsequently, pyrroles have been highlighted as the important biologically active scaffolds. This review focuses on the synthesis, reactions and pharmacological activity associated with pyrroles, and its derivatives. Microwave-assisted reactions are also covered to understand green chemistry aspects of pyrrole and its derivatives. Various pharmacological applications are discussed critically to assess the importance of the compounds.
8. Aromaticity in Polyacenes and Their Structural Analogues
Author(s): Ranjita Das, Arindam Chakraborty, Sudip Pan and Pratim K. Chattaraj
Affiliation: Department of Chemistry and Center for Theoretical Studies, Indian Institute of Technology Kharagpur, 721302, India.
The successful synthesis of different polyacenes including theoretical assessment on the stability of larger acenes are discussed. The existence of favorable aromaticity criterion in polyacenes is understood in terms of different aromaticity indicators like nucleus independent chemical shift (NICS), harmonic oscillator model of aromaticity (HOMA), bond resonance energy (BRE). Clar’s Π- sextet rule is also very much effective in explaining their aromaticity. By virtue of low HOMO-LUMO gap, the probable application of polyacenes in the field of organic electronics is also highlighted. The polyacene analogues of inorganic ring compounds, viz., BN-acenes, CN-acenes, BO-acenes, BS-acenes, AlN-acenes and of alkali ring compounds, viz., Na-acenes and K-acenes also have polyacene-like aromaticity although in few cases the origin of aromaticity and qualitative nature of aromaticity differ significantly.