Stereoselektive Bildung von Halbacetalen des <i>cis</i>‐2,3‐Dimethylcyclopropanons aus 2‐Halogen‐3‐pentanonen. [4 + 3]‐Cycloadditionen an konjugierte Dien‐Systeme

Föhlisch, Baldur; Gehrlach, E.; Stezowski, John J.; Kollat, P.; Martin, Eveline; Gottstein, W.

doi:10.1002/cber.19861190518

Cited by 27 publications

(14 citation statements)

References 42 publications

(1 reference statement)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The exception are “2‐oxyallyls” that form part of a C 5 ring: in other words, 2‐oxido‐2‐cyclopenten‐1‐ylium compounds, which, according to high‐level theoretical calculations38−42 and experimental evidence43,44 are energetically more stable than their cyclopropanone counterparts. Therefore, 2‐oxido‐2‐cyclopenten‐1‐ylium compounds are more likely to exhibit clean oxyallyl chemistry uncontaminated by cyclopropanone chemistry (such as hemiacetal formation,36 Favorskii rearrangement,45 or cycloaddition to the carbonyl group18). 35…”

Section: Introductionmentioning

confidence: 99%

The Addition of 2-Oxido-2-cyclopenten-1-ylium to Some Olefins and Dienes in 2,2,2-Trifluoroethanol

Leitich

Heise

2001

Eur. J. Org. Chem.

View full text Add to dashboard Cite

The title reaction has been studied with 2‐methoxypropene, (E)‐cyclooctene, ethoxyethene, 1,3‐cyclopentadiene, 3‐methylenecyclohexene, styrene and isoprene as the olefinic substrates. This sequence is one of decreasing reactivity of the substrates towards 2‐oxido‐2‐cyclopenten‐1‐ylium (1) if [4 + 3] cycloaddition (the prevailing reaction in the case of cyclopentadiene and isoprene) is ignored. This reactivity encompasses: (a) the formation of intermediate 1,5‐dipoles, which in the majority of cases give rise to a multitude of products including many of higher molecular mass, and (b) two types of ene reactions, dubbed “ene‐type 1” and “ene‐type 2”. Type 1, in which the migrating hydrogen atom is abstracted from 1, is ubiquitous (except with 2‐methoxypropene) but is always a minor reaction; type 2, in which the migrating hydrogen atom is transferred to 1, was encountered only in the cases of 3‐methylenecyclohexene, in which it is a major reaction path, and isoprene. Both types were found to be slightly concerted. In this context, we observed an effect which we have dubbed “dipolar diversion of a concerted reaction”. In general, those substrates incapable of forming [4 + 3] cycloadducts gave complicated mixtures, with the exception of two compounds, which were found to give one predominant product with 1. The first of these is the trans‐fixed 1,3‐diene 3‐methylenecyclohexene, which gave the ene‐type 2 adduct 10d1, while the second is the most nucleophilic substrate, 2‐methoxypropene, which gave a mixture of four adducts (two pairs of epimers), all of which gave the diketone 17 on hydrolysis.

show abstract

Section: Introductionmentioning

confidence: 99%

The Addition of 2-Oxido-2-cyclopenten-1-ylium to Some Olefins and Dienes in 2,2,2-Trifluoroethanol

Leitich

Heise

2001

Eur. J. Org. Chem.

View full text Add to dashboard Cite

show abstract

“…[29] A rationalization of the stereochemistry of oxyallyl formation has been given. [10] Finally, cycloadditions between furan and the oxyallyls generated from 2,4-dichloro-and dibromo-pentan-3-one or 1,1,3,3-tetrachloroacetone take the same stereochemical course, as the endo-isomers are formed preferentially. [13,30] The diminished endo-exo-selectivity points to a two-step cycloaddition.…”

Section: Resultsmentioning

confidence: 98%

“…A, from 2-bromo and 2-chloro-3-pentanone, which is structurally equivalent to 1,3-dibromo-2-butanone, was demonstrated years ago by our group. [10] Chloro-and bromo-substituted oxyallyl intermediates derived from a few acyclic dihalogeno ketones having secondary or tertiary α-carbon atoms could be trapped by cycloaddition to, e.g., furan using lithium perchlorate/triethylamine in diethyl ether or fluorinated alcohols in the presence of bases, e.g. sodium 2,2,2-trifluoroethoxide in trifluoroethanol (NaTFE/TFE).…”

Section: Introductionmentioning

confidence: 99%

Base‐Induced Trifluoroethanolysis of Acyclic Di‐ and Trihalogeno Ketones: Favorskii Rearrangement and [4+3] Cycloaddition

Föhlisch¹,

Franz²,

Kreiselmeier³

2005

Eur J Org Chem

Self Cite

View full text Add to dashboard Cite

Reactions of five acyclic dihalogeno‐ and trihalogeno ketones, representing the α,α‐, α,α′‐, α,α,α‐ and α,α,α′‐di‐ and trihalogeno substitution pattern, with sodium 2,2,2‐trifluoroethoxide in 2,2,2‐trifluoroethanol (NaTFE/TFE) in the presence of furan were investigated with the aim of obtaining [4+3] cycloadducts of the corresponding oxyallyl intermediates. Preference of Favorskii rearrangement over cycloaddition was observed with dichloromethyl isobutyl ketone (1a) and 1,3‐dibromobutan‐2‐one (12) that formed mainly the trifluoroethyl esters of 3‐chloro‐2‐isopropylpropanoic acid (9a), and (Z)‐but‐2‐enoic acid (isocrotonic acid) (13), respectively. 9a was dehydrohalogenated to form trifluoroethyl 3‐isopropylacrylate (11a). [4+3] Cycloaddition was favored with the 1,1,3‐trihalogenobutan‐2‐ones 24 and 25, leading to 2,4‐dihalogenated 8‐oxabicyclo[3.2.1]oct‐6‐en‐3‐ones (26, 27) as a mixture of endo‐exo‐stereoisomers. With trichloromethyl isobutyl ketone (30) the isomeric 2,4‐dichloro‐substituted oxabicycles (34) were formed in lithium perchlorate/diethyl ether/furan/triethylamine, while in NaTFE/TFE solvolytic displacement of one chloro substituent occurred, providing 2‐chloro‐4‐trifluoroethoxy‐4‐isopropyl‐8‐oxabicyclo[3.2.1]oct‐6‐en‐3‐one (36). By analogy, 27 reacted with sodium methoxide/methanol to form the methoxy‐substituted oxabicycles 39a and 39b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

show abstract

“…(ii) 9-Ethyl-9-(2,2,2-trifluoroethoxy)fluorene (5b) (2%) d H (500 MHz; CDCl 3 ) 7.30-7.82 (m, 8H), 3.60 (2H, q, J9.0), 2.37 (3H, q, J7.5), 0.92 (3H, t, J7.5); GC-MS (m/z): 263 (100), 193 (5), 180 (55), 152 (30), 57 (30).…”

Section: Photolysis General Proceduresmentioning

confidence: 99%

“…(iv) 1-(9-Fluorenyl)-1-propanone 34 (7b) (28%) d H (500 MHz; CDCl 3 ) 7.30-7.84 (8H, m), 5.05 (1H, s), 3.56 (2H, q, J7.5), 0.96 (3H, t, J7.5); GC-MS (m/z): 222 (15), 207 (3), 165 (65), 139 (10), 57 (100). (ii) 9-Pentyl-9-(2,2,2-trifluoroethoxy)fluorene (5c) (40%) GC-MS (m/z): 334 (5), 263 (100), 180 (30), 178 (25) 152 (15).…”

Section: Photolysis General Proceduresmentioning

confidence: 99%

Effect of steric bulk on the absolute reactivity of allene oxides

Konecny

Schepp

2009

Org. Biomol. Chem.

View full text Add to dashboard Cite

Alpha-alkyl substituted fluorenylidene allene oxides were generated photochemically from appropriately substituted fluorenol derivatives in 2,2,2-trifluoroethanol (TFE) in order to assess the affect of steric bulk on the absolute reactivity of the allene oxides. The absolute reactivities of the allene oxides were measured using nanosecond laser flash photolysis, and were found to change little in TFE upon going from alpha-methyl to alpha-butyl to alpha-t-butyl. However, all three alpha-alkyl substituted allene oxides were considerably more reactive than the alpha-hydrogen derivative, indicating that steric bulk did not result in a decrease in reactivity as is typically found in other allene oxides. The contrary reactivity of the fluorenylidene allene oxides is explained by examining in detail the reactions of these allene oxides, determined from product studies.

show abstract

Stereoselektive Bildung von Halbacetalen des cis‐2,3‐Dimethylcyclopropanons aus 2‐Halogen‐3‐pentanonen. [4 + 3]‐Cycloadditionen an konjugierte Dien‐Systeme

Cited by 27 publications

References 42 publications

The Addition of 2-Oxido-2-cyclopenten-1-ylium to Some Olefins and Dienes in 2,2,2-Trifluoroethanol

The Addition of 2-Oxido-2-cyclopenten-1-ylium to Some Olefins and Dienes in 2,2,2-Trifluoroethanol

Base‐Induced Trifluoroethanolysis of Acyclic Di‐ and Trihalogeno Ketones: Favorskii Rearrangement and [4+3] Cycloaddition

Effect of steric bulk on the absolute reactivity of allene oxides

Contact Info

Product

Resources

About