Desulfonylation reactions: Recent developments

The Diels–Alder (“DA”) reaction is so familiar to organic chemists that the retro-Diels–Alder or retro-diene reaction (hereafter “rDA”) requires no conceptual introduction. However, a working definition is needed to indicate the coverage of this review. The intent is to include all reported examples of the general skeletal process excluded in this chapter.



Any of the atoms in the starting material (cycloadduct) may be carbon or heteroatom, and substituents on all positions are allowed. In addition, any bond order available to the element in any oxidation state is included, as well as bonding to non-nearest neighbor atoms (bicyclics, etc.).



The volume of literature required separation of this review into two parts. Part I covers all expelled C–C dienophiles, i.e. those reactions that generate a new carbon-carbon double or triple bond in the dienophile that is formed. Part II, to appear later, covers those expelled dienophiles in which one or both atoms is a heteroatom.



Certain specific topics are intentionally omitted. These are: rDA reactions invoked under mass spectral conditions; rDA reactions of polymeric substrates; Electrocyclic processes, some of which are arguably very similar to rDA reactions (these are not addressed unless needed for clarification of an rDA sequence); and a thorough discussion of homo-rDA reactions.



CAS-Online searches resulted in ca. 1,300 references, of which ca. 900 proved pertinent to the rDA topic as defined and delimited above. Active literature searching was halted in April 1995, but occasional more recent articles are included.



Over 2,500 pertinent references were eventually found. Most were obtained by perusal of primary literature (articles) and secondary sources (books and reviews). Computer based search success was limited mainly by the failure of authors or abstractors to key-word this topic, an especially common occurrence when the expelled dienophile was a simple substance such as N2 or CO2. Overall, approximately 3,500 books, chapters, reviews, articles, and abstracts were consulted in an effort to make this review as comprehensive as possible. This was done with the certainty that some pertinent literature would be missed, tempered by the view that these omissions are probably also lost to any future rational search method.



Many secondary sources proved valuable not only for in-depth discussion of certain rDA reaction types, but also for providing comparisons with related topics. To assist the reader, these secondary sources are referenced (alphabetically by first author within broad subject areas) with a title or brief note on the topic(s) addressed. The first group lists earlier reviews with primary focus on rDA reactions, followed by items of Historical/General Interest, reviews that deal with Experimental Methods, DA reactions (general and specific), reviews of Related Topics (these impinge in more or less significant ways on rDA reactions), and general treatments of Theory and Mechanism.


Keywords:

retro Diels-Alder reactions;
dienophiles;
mechanism;
scope;
limitations;
acid catalysis;
base induced reactions;
scavengers;
reactivity comparisons;
acetylenic dienophiles;
alkyl ethylenes;
alkyl alkenes;
aryl substituted alkenes;
vinyl substituted alkenes;
heteroatom substituted alkenes;
ketenes;
experimental conditions;
tabular survey

The Retro–Diels–Alder Reaction Part I. C ? C Dienophiles

Recent advances in the synthesis of indan systems. a review

The 2,5-disubstituted thienosultines (5,7-disubstituted 1,4-dihydro-1H-3λ4-thieno[3,4-d][2,3]oxathiin-3-oxides) 5a−d were prepared from the corresponding dichlorides 4a−d with the commercially available Rongalite (sodium formaldehyde sulfoxylate) in 17−60% yields. When heated in the presence of electron-poor dienophiles, sultines 5a−d underwent elimination of SO2, and the resulting non-Kekule biradicals 7a−d were intercepted as the 1:1 adducts 8−12 in good to excellent yields. The pyrolysis of sultines and sulfolenes with different concentrations of dienophiles revealed that either a preequilibrium between starting reagents and biradical species or Diels−Alder and retro-Diels−Alder reaction mechanisms may be involved; however, more work is necessary to establish the proposed mechanisms. Reaction of sultine 5b with nBuLi was found to undergo a nucleophilic ring-opening reaction to give sulfinyl alcohol 17 after H2O workup. When sultine 5a was heated in benzene in a sealed tube in the presence of methanol, ...

https://ir.nctu.edu.tw:443/bitstream/11536/28303/1/000180072300019.pdf

Synthesis of 2,5-disubstituted thienosultines and their thermal reactions with dienophiles and nucleophiles.

Publisher Summary o -Quinodimethane and derivatives have been extensively studied. They are reactive dienes that can be generated in situ by a number of routes; their inter and intramolecular Diels–Alder reactions have been the basis of the synthesis of a wide range of target molecules including steroids, alkaloids, and anthracyclines. In spite of their considerable potential in synthesis, heterocyclic analogues have received much less attention. However, the situation has changed considerably and the ground rules for producing and handling such species have become much clearer. This chapter presents an overview of their chemistry and methods of generation, and intends to stimulate the use of these species in synthesis.

Chapter 2 Heterocyclic ortho-quinodimethanes

4H,6H-thieno[3,4-c]furan 5,5-dioxide 1 was readily converted to the 4-alkylated compounds 2 and the appropriate compounds 2 were submitted to intramolecular Diels–Alder reactions to afford fused furans 8a and b in good yields.

Alkylation of 4H,6H-thieno[3,4-c]furan 5,5-dioxide and its use as a 3,4-dimethylenefuran synthon in intramolecular Diels–Alder reactions

Alkylation of 4H,6H-thieno[3,4-c]furan 5,5-dioxide (furan-annulated sulfolene)1 readily gave its 4-alkyl, 4,6-dialkyl, or 4,4-dialkyl derivatives, selectively. Attempts were made to use the appropriate derivatives as 3,4-dimethylenefuran synthons in intramolecular Diels–Alder reactions. Thus when they were heated after treatment with methyl vinyl ketone, a Diels–Alder reaction with methyl vinyl ketone on the furan moiety, desulfonylation, intramolecular Diels–Alder reaction of the resulting dienes, and retro Diels–Alder reaction occurred sequentially to afford the tricyclic fused furans 17a–c; in good yields.

Alkylation of 4H,6H-thieno[3,4-c]furan 5,5-dioxide and its use as a 3,4-dimethylenefuran synthon in intramolecular Diels–Alder reaction

4-Acyl-4H,6H-thieno[3,4-c]furan 5,5-dioxides have been prepared and submitted to Diels–Alder reactions to afford dienes with greater steric congestion after desulfonylation.

Novel formation of dienes with greater steric congestion resulting from the Diels–Alder reaction–desulfonylation sequence of 4-acyl-4H,6H-thieno[3,4-c]furan 5,5-dioxides

Novel Formation of Dienes with Greater Steric Congestion Resulting from the Diels-Alder Reaction-Desulfonylation Sequence of 4-Acyl-4H,6H- thieno(3,4-c)furan 5,5-Dioxides.

Naoki Akadegawa

Papers

Alkylation of 4H,6H-thieno[3,4-c]furan 5,5-dioxide and its use as a 3,4-dimethylenefuran synthon in intramolecular Diels–Alder reactions

Alkylation of 4H,6H-thieno[3,4-c]furan 5,5-dioxide and its use as a 3,4-dimethylenefuran synthon in intramolecular Diels–Alder reaction

Novel formation of dienes with greater steric congestion resulting from the Diels–Alder reaction–desulfonylation sequence of 4-acyl-4H,6H-thieno[3,4-c]furan 5,5-dioxides

Novel Formation of Dienes with Greater Steric Congestion Resulting from the Diels-Alder Reaction-Desulfonylation Sequence of 4-Acyl-4H,6H- thieno(3,4-c)furan 5,5-Dioxides.

Alkylation of 4H,6H‐Thieno(3,4‐c)furan 5,5‐Dioxide and Its Use as a 3, 4‐Dimethylenefuran Synthon in Intramolecular Diels‐Alder Reactions.