Microwave-Assisted Tandem Wittig—Intramolecular Diels—Alder Cycloaddition. Product Distribution and Stereochemical Assignment.

ChemInform ◽  
2006 ◽  
Vol 37 (52) ◽  
Author(s):  
Jinlong Wu ◽  
Lijie Sun ◽  
Wei-Min Dai
Keyword(s):  
Product Distribution ◽  
Diels Alder ◽  
Stereochemical Assignment ◽  
Microwave Assisted ◽  
Cycloaddition Product

Silaheterocyclen, XXIV. / Silaheterocycles, XXIV.

1993 ◽  
Vol 48 (3) ◽  
pp. 318-332 ◽  
Author(s):  
Norbert Auner ◽  
Armin W. Weingartner ◽  
Eberhardt Herdtweck
Keyword(s):  
Energy Levels ◽  
Cycloaddition Reaction ◽  
Product Distribution ◽  
Diels Alder ◽  
Frontier Molecular Orbitals ◽  
X Ray Diffraction ◽  
Insertion Reactions ◽  
Ene Reaction ◽  
X Ray ◽  
Cycloaddition Product

The 1-amino-2-neopentylsilenes 5-8 are formed in the reaction of LitBu with the aminovinylsilanes 1-4 in n-pentane (addition of LitBu to the vinylic double bond with subsequent 1,2-elimination of LiCl). The α-Li adducts initially formed are trapped by Me3SiOSO2CF3 to yield α-SiMe3-silanes. The silenes undergo insertion reactions into the Si—O bond of Me3SiOMe. In the absence of any trapping reagent dimerization occurs. One of the 1,3-disilacyclobutanes thus formed (15) could be examined by X-ray diffraction. Reacting with 1,3-butadienes the chlorosubstituted silenes 5 and 8 yield [2 + 2]-cycloaddition products. With 1,3-cyclohexadiene Diels-Alder adducts are also obtained, but with cyclopentadiene the [4+2] adducts are formed exclusively. Products of an ene-reaction are observed upon treatment of 2,5-norbornadiene with the silenes 5 and 8.The methylsubstituted silene 6 does not undergo any cycloaddition reaction at all, while from silene 7 only traces of the cycloadducts are produced. Both species mainly yield the dimers. The preference for the [2+2] reaction type, exhibited by the silenes 5 and 8, is due to their polarity. The almost complete absence or low yield of any cycloaddition products from 6 or 7 can be correlated with the energy levels of their frontier molecular orbitals. The distribution of the disilacyclobutanes and cycloaddition product isomers is explained by the characteristics of the stereospecifically Ε-configurated silenes. The product distribution can also be rationalized considering the ambiphilic nature of the system ViRR′SiCl/Li1Bu.

Microwave-assisted co-pyrolysis of Chlorella vulgaris and Polypropylene: Characteristic and product distribution analyses

2021 ◽  
pp. 126279
Author(s):  
Chunxiang Chen ◽  
Jian Zhao ◽  
Dianzhao Fan ◽  
Qianhao Qi ◽  
Tianyang Zeng ◽  
...  
Keyword(s):  
Chlorella Vulgaris ◽  
Product Distribution ◽  
Microwave Assisted

Recyclable organotungsten Lewis acid and microwave assisted Diels–Alder reactions in water and in ionic liquids

Tetrahedron ◽  
2004 ◽  
Vol 60 (51) ◽  
pp. 11903-11909 ◽  
Author(s):  
I-Hon Chen ◽  
Jun-Nan Young ◽  
Shuchun Joyce Yu
Keyword(s):  
Ionic Liquids ◽  
Lewis Acid ◽  
Diels Alder ◽  
Microwave Assisted

Complex Reactions

2001 ◽  
Author(s):  
L. K. Doraiswamy
Keyword(s):  
Organic Synthesis ◽  
Product Distribution ◽  
Diels Alder ◽  
Point Of View ◽  
Complex Reaction ◽  
Design Point ◽  
Multiple Reactions ◽  
Practical Strategy ◽  
Multistep Reactions ◽  
Quantitative Treatment

When a reactant or a set of reactants undergoes several reactions (at least two) simultaneously, the reaction is said to be a complex reaction. The total conversion of the key reactant, which is used as a measure of reaction in simple reactions, has little meaning in complex reactions, and what is of primary interest is the fraction of reactant converted to the desired product. Thus the more pertinent quantity is product distribution from which the conversion to the desired product can be calculated. This is usually expressed in terms of the yield or selectivity of the reaction with respect to the desired product. From the design point of view, an equally important consideration is the analysis and quantitative treatment of complex reactions, a common example of which is the dehydration of alcohol represented by We call such a set of simultaneous reactions a complex multiple reaction. It is also important to note that many organic syntheses involve a number of steps, each carried out under different conditions (and sometimes in different reactors), leading to what we designate as multistep reactions (normally called a synthetic scheme by organic chemists). This could, for example, be a sequence of reactions like dehydration, oxidation, Diels-Alder, and hydrogenation. This chapter outlines simple procedures for the treatment of complex multiple and multistep reactions and explains the concepts of selectivity and yield. For a more detailed treatment of multiple reactions, the following books may be consulted: Aris (1969) and Nauman (1987). We conclude the chapter by considering a reaction with both catalytic and noncatalytic steps, which also constitutes a kind of complex reaction. Because both chemists and chemical engineers are involved in formulating a practical strategy for accomplishing an organic synthesis, it is important to appreciate the roles of each.

Microwave-assisted Diels–Alder polycondensation of proton conducting poly(phenylene)s

2019 ◽  
Vol 10 (13) ◽  
pp. 1668-1685 ◽  
Author(s):  
Michael Adamski ◽  
Thomas J. G. Skalski ◽  
Shaoyi Xu ◽  
Miho Killer ◽  
Eric M. Schibli ◽  
...  
Keyword(s):  
Reaction Time ◽  
Microwave Synthesis ◽  
Diels Alder ◽  
Proton Conducting ◽  
Microwave Assisted ◽  
Fold Reduction ◽  
Sulfonated Poly

A 24-fold reduction in reaction time is achieved in the preparation of sulfonated poly(polyphenylene)s using microwave synthesis.

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