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Special Topic Sulfur Going beyond the bad smell… Gaëlle Mingat 10/10/12 1.

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Presentation on theme: "Special Topic Sulfur Going beyond the bad smell… Gaëlle Mingat 10/10/12 1."— Presentation transcript:

1 Special Topic Sulfur Going beyond the bad smell… Gaëlle Mingat 10/10/12 1

2 Sulfur, going beyond the bad smell… Overview 10/10/12 2 I.General properties II.Some name reactions involving sulfur III.Sulfur ylides and the Corey-Chaykovsky reaction IV.Chiral sulfur V.Sulfur migration in organic synthesis VI.Sulfur in the food industry VII. A « bad smell » example, just one… VIII.Sulfur in perfumes

3 3 I. General properties - abundant, multivalent non-metal - cyclic octatomic molecule: S 8 Bright yellow solid - Either an oxidant or a reducing agent - Found in nature as the pure element, sulfide (S 2- ) and sulfate (SO 4 2- ) minerals Melting point: °C, blood-red liquid Burns with a blue flame better observed in the dark

4 4 I. General properties Carrying sulfur blocks from a volcano, Indonesia - Once extracted from salt domes: Frasch process → 99.5% pure melted product - Today produced as a by-product by removing organosulfur compounds from natural gas and petroleum Hydrodesulfurization R-S-R + 2H 2 → 2 R-H + H 2 S Conversion of hydrogen sulfide in elemental sulfur via the Claus process 3 O H 2 S → 2 SO H 2 O SO H 2 S → 3 S + 2 H 2 O World production in 2011: 69 M tones → China (9.6), US (8.8), Canada (7.1), Russia (7.1) Stockpiles of elemental sulfur recovered from hydrocarbons, Alberta, Canada Dibenzothiophene, a composant of crude oil

5 5 I. General properties Electronic configurations: 6 C 1s 2 2s 2 2p 2 8 O 1s 2 2s 2 2p 4 16 S 1s 2 2s 2 2p 6 3s 2 3p 4 O: r = 70.2 pm S: r = pm C-O: kJ/mol C-S: 255 kJ/mol C=O: 678 kJ/mol C=S: 377 kJ/mol Longer and weaker  bond Weaker π bond (bad overlap) Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105)

6 6 → electron affinities, ionization potentials, bond energies  C-S bond: polarization not pronounced  Ionic character lessened as compared to oxygen counterparts (hydrogen bonding less important) Sanderson: «compactness » of an atom’s electron cloud → Polarizability of S  Aromaticity: furan (E res = 75kJ/mol) < thiophene < benzene (E res = 113 kJ/mol) I. General properties Electronegativities Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105)

7 7 I. General properties Essential element for life 7 Cysteine Cystine (dehydrogenated cysteine) Methionine Glutathione : antioxydant (Cysteine/Glycine/Glutamate) Disulfide bonds : mechanical strength, insolubility of keratin (hair, outer skin, feathers) and pungent odor when burned Thioester acetyl coenzyme A

8 8 I. General properties Essential element for life 8 Thiamine (vitamin B1) Umpolung chemistry in nature Penicillin core structure « S-adenosylmethionine »: Nature’s iodomethane or diazomethane equivalent Biotin (vitamin H) Sulfanilamide (sulfa drug)

9 9 Thiols: R-SHSulfides: R-S-R SulfoxidesSulfonesSulfonic acids SulfimidesSulfoximidesSulfonediimides Thiocarbonyls: thioamides Sulfinic acids Sulfonamides (sulfa drugs) SulfinamidesSulfenamides I. General properties Sulfenic acids Important chemical functionalities

10 10 S-nitrosothiolsIsothiocyanates Sulfonium, oxosulfonium ionSulfonium, oxosulfonium ylide Sulfines Thiocyanates [R 3 S] + I. General properties Important chemical functionalities

11 11 II. Some name reactions involving sulfur - Oxidation reactions → Pfitzner-Moffatt ▫ urea byproducts difficult to remove → Swern ▫ better yields, fewer side products than P-M → Corey-Kim ▫ T > -25°C allowed but Me 2 S (toxic + bad smell) - Sulfur as a reducing agent → NaHSO 3, Na 2 SO 3, Na 2 S 2 O 3, Na 2 S·9H 2 O, SOCl 2, SO 2... → Me 2 S in ozonolysis to prevent further oxidation of products (still used??) - Lawesson’s reagent: from a ketone to a thioketone → Enones, esters, lactones, amides, lactams, quinones Kürti L., Czako B.; Strategic Applications of Named Reactions in Organic Synthesis (2005)

12 12 II. Some name reactions involving sulfur - Oxidation reactions → Davis’ oxaziridine oxidations ▫ 2-arylsulfonyl-3-aryloxaziridines ▫ sulfides and selenides to sulfoxides and selenoxides ▫ alkenes to epoxides ▫ amines to hydroxylamines and amine oxides ▫ organometallic compounds to alcohols and phenols ▫ most widespread application: oxidation of enolates to α-hydroxy carbonyl compounds (acyloins) Kürti L., Czako B.; Strategic Applications of Named Reactions in Organic Synthesis (2005)

13 13 II. Some name reactions involving sulfur - Olefinations → Bamford Stevens ▫ aprotic solvents: Z-alkenes major / protic solvents: mixture of E- and Z-alkenes → Shapiro → Corey-Winter → Julia-Lythgoe ▫ E-alkenes major Kürti L., Czako B.; Strategic Applications of Named Reactions in Organic Synthesis (2005)

14 14 II. Some name reactions involving sulfur - Rearrangements → Mislow-Evans → Pummerer → Ramberg-Bäcklund → Stevens ▫ 1,2-rearrangement of a sulfonium salt giving a sulfide, using a strong base Kürti L., Czako B.; Strategic Applications of Named Reactions in Organic Synthesis (2005)

15 15 → Barton-McCombie radical deoxygenation reaction ▫ radical substitution via a thiocarbonyl → Burgess dehydration reaction → Chugaev elimination reaction ▫ alkenes from alcohols via a xanthate undergoing a syn-elimination → Corey-Nicolaou macrolactonization II. Some name reactions involving sulfur Kürti L., Czako B.; Strategic Applications of Named Reactions in Organic Synthesis (2005)

16 16 III. Sulfur ylides and the Corey-Chaykovsky reaction Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105)

17 17 Corey-Chaykovsky reaction: JACS 1965, 87 (6), 1353 III. Sulfur ylides and the Corey-Chaykovsky reaction Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105)

18 18 Enantio- and diastereocontrol in sulfur ylides-mediated epoxidations: Aggarwal’s work III. Sulfur ylides and the Corey-Chaykovsky reaction Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105) Aggarwal V.; Chem. Commun. 2003, 2644

19 19 III. Sulfur ylides and the Corey-Chaykovsky reaction Examples of sulfur ylides mediated asymmetric epoxidations Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105) Aggarwal V.; Chem. Commun. 2003, 2644

20 20 The example of stabilized ylides (additional anion-stabilizing group) : trans-diastereoselectivity Cross-over experiments:  Either anti- or syn-sulfonium salt furnishes only the trans-epoxide containing the more reactive aldehyde (p-NO 2 C 6 H 4 ) → both syn- and anti-betaine are formed reversibly  Trans-selectivity because barrier to torsional rotation in anti-betaine smaller III. Sulfur ylides and the Corey-Chaykovsky reaction Aggarwal V.; Chem. Commun. 2003, 2644

21 21 Semi-stabilized ylides: trans-diastereoselectivity Cross-over experiments:  Anti-betaine reacted with a more reactive aldehyde: no incorporation of this aldehyde in the final epoxide  With syn-betaine: complete incorporation of the more reactive aldehyde → Anti-betaine irreversibly formed → Syn-betaine reversibly formed III. Sulfur ylides and the Corey-Chaykovsky reaction Aggarwal V.; Chem. Commun. 2003, 2644

22 22 Control of enantioselectivity 1)Formation of a single diastereoisomeric sulfonium ylide 2)High level of control of ylide conformation 3)High level of control in face selectivity of the ylide 4)Non-reversibility of the anti-betaine formation III. Sulfur ylides and the Corey-Chaykovsky reaction Aggarwal V.; Chem. Commun. 2003, 2644

23 23 Control of enantioselectivity: effect of protic solvents If low enantioselectivity: Protic solvents or addition of Li cations makes the reaction less reversible (if reversibility of betaine formation is the cause) If low diastereoselectivity: Aprotic solvents and avoidance of species capable of solvating alkoxides (increase of rotation barrier so reaction more reversible – displacement equilibrium to left) III. Sulfur ylides and the Corey-Chaykovsky reaction Aggarwal Aggarwal V.; Chem. Commun. 2003, 2644

24 24 IV. Chiral sulfur Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105 )

25 25 IV. Chiral sulfur Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105 )

26 26 IV. Chiral sulfur Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105 )

27 27 IV. Chiral sulfur Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105 )

28 28 IV. Chiral sulfur Schaumann E.; Top Curr. Chem. 2007, 274:1-34 (DOI /128_2006_105 )

29 29 Stuart Warren’s work; preliminary observation V. Sulfur migration in organic synthesis Warren S.; Phosphorous, Sulfur and Silicon 1999, , 59

30 30 D. House, S. Warren: stereospecificity in the migration of « SPh » V. Sulfur migration in organic synthesis Secondary OH = LG Primary OH = Nu Secondary OH = LG Primary OH no more a Nu Warren S.; Phosphorous, Sulfur and Silicon 1999, , 59

31 31 Competition between 2 hydroxyl groups Is it possible to control which OH leaves, which acts as a Nu and where it attacks?? Primary OH = LG SPh = Nu Primary OH = LG Secondary OH = Nu V. Sulfur migration in organic synthesis Warren S.; Phosphorous, Sulfur and Silicon 1999, , 59

32 32 Kinetic resolution of racemic and enolisable 2-PhS aldehydes V. Sulfur migration in organic synthesis Warren S.; Phosphorous, Sulfur and Silicon 1999, , 59

33 33 VI. Sulfur in the food industry  About 10% of the volatile components detected in foods and beverages contain sulfur  Volatile organic sulfur compounds: extremely low odour threshold → highly important for flavours and aromas Goeke A.; Sulfur reports 2002, 23, 3, 243

34 34 VI. Sulfur in the food industry The Maillard reactions (1911) ▫ chemical reactions occuring while cooking food ▫ amino acids + sugars form a brownish mixture when heated to high temperature ▫ responsible for many colors and flavors in foods: - the browning of various meats like steak - toasted bread, burnished crust of brioche, cakes, yeast, biscuits - French fries, fried onions - malted barley (whiskey, beer) - dried or condensed milk (dulce de leche) - maple syrup - roasted coffee ▫ importance for the food industry in order to control the aspect, the taste and the conservation of food (incorrect preparation or storage produce off-flavours)

35 35 VI. Sulfur in the food industry Role of cysteine and cysteine-S conjugates as odour precursors Maillard reaction: cysteine + sugars (meat flavour…) Roast meatPopcornBasmati rice  Cheddar cheese: methanethiol, hydrogen sulfide, dimethyl disulfide, dimethyl trisulfide → products of the catabolism of methionine and cysteine by bacteria Starkenmann C.; Flavour Fragr. J. 2008, 23, 369

36 VI. Sulfur in the food industry Role of cysteine and cysteine-S conjugates as odour precursors  Wine and passion fruit Wine treated with copper sulfate → « boxtree » and « tropical fruit » odours disappeared Aroma of young botrytized sweet wines Passion fruit aroma Cysteinylated precursors to typical aroma of Sauvignon wines 36 Starkenmann C.; Flavour Fragr. J. 2008, 23, 369

37 VI. Sulfur in the food industry Sulfur compounds in wine → 5 families: thiols, sulfides, polysulfides, thioesters, heterocycles → 2 categories: boiling point below or above 90 °C (volatile compounds or less) → Produced by 2 main processes:  enzymatic: degradation of sulfur-containing amino-acids fermentation metabolism of sulfur-containing pesticides  non-enzymatic:photochemical, thermal, chemical reactions during winemaking and storage → Role of SO 2 : antibiotic and antioxydant (« contains sulfites »; up to 10mg/L) → Reactions most studied: those catalyzed by light and producing unpleasant flavours called « light tastes » or « reduced tastes » 37 Guasch J.; J. Chromath. A 2000, 881, 569

38 38 VI. Sulfur in the food industry Guasch J.; J. Chromath. A 2000, 881, 569

39 39 VI. Sulfur in the food industry

40 40 VI. Sulfur in the food industry

41 41 VI. Sulfur in the food industry  In general, aromatic contributions of the above compounds considered detrimental to wine quality → cabbage, garlic, onion, rubber…  Some sulfur compounds contribute actively and are typical to some wine aromas → strawberry → box tree → passion fruit → cooked leeks Sulfur compounds in wine Guasch J.; J. Chromath. A 2000, 881, 569

42 VII. A « bad smell » example, just one… → Human sweat A tertiary thiol… Sweat secreted by axillary glands odourless: odoriferous components generated by skin bacteria 42 Starkenmann C.; Flavour Fragr. J. 2008, 23, 369

43 43 VIII. Sulfur in perfumes - Sulfur-containing compounds: some of the strongest odorants - Perception of odor often depends on: → chemical, diastereo- and enantio-purity → concentration (unpleasent odor when smelled at high concentration) ▫ ability to trigger different receptor sites in the olfactory bulb of the nose The cassis/cat example: 4-mercapto-4-methylpentanone 29 > 0.001%: obnoxious tom-cat urine off-odor (0.4% impurity in paint) < %: natural crisp cassis note (Sauvignon wines) Also « Baie rouge » scent (raspberry), box tree, broom, green tea, grapefruit Goeke A.; Sulfur reports 2002, 23, 3, 243

44 44 VIII. Sulfur in perfumes  Importance of steric bulk around sulfur group (tertiary mercapto ketones)  Structure-odor correlations Free tertiary sulfur group distant of 2-4 Å of a carbonyl  Importance of H bonding 61: no fruity odor 62: less cassis-like than 63 Goeke A.; Sulfur reports 2002, 23, 3, 243

45 45 VIII. Sulfur in perfumes  Importance of diastereo- and enantio- purity  Hydrolysis of thioacetates in the mucosa of the olfactory bulb responsible for cassis odor in 38? Goeke A.; Sulfur reports 2002, 23, 3, 243

46 46 VIII. Sulfur in perfumes Grapefruit 1982: 1-p-menthene-8-thiol shown to be an extremely potent constituent of grapefruit juice. Also identified in orange, yuzu and must.

47 47 VIII. Sulfur in perfumes Passionfruit Oxane ® (perfumery) 62, 63: also in white and red wines Goeke A.; Sulfur reports 2002, 23, 3, 243

48 48 VIII. Sulfur in perfumes Green scents Fancy « tomato leaves » scent in the perfume « Les Belles » (Nina Ricci): complex combination of several odorants. Essential oil of coriander, used in fine fragrances: « Gucci No. 1 », « Le Jardin d’Amour », « Coriandre » (!) Goeke A.; Sulfur reports 2002, 23, 3, 243

49 49 VIII. Sulfur in perfumes Scents of flowers Goeke A.; Sulfur reports 2002, 23, 3, 243

50 50 VIII. Sulfur in perfumes The archetypal example: rose oil Impart naturalness of rose scent perceived when smelling rose petals to essential rose oil Goeke A.; Sulfur reports 2002, 23, 3, 243

51 51 VIII. Sulfur in perfumes Musk odors - macrocyclic lactones and ketones: core structures found in natural isolates (muscone, ambrettolide, pentadecanolide) - quality of musk odor and intensity depends on: ▫ a subtle equilibrium of the ring size and geometry with hydrophobic parts and hydrogen-bond acceptors ▫ position of sulfur atom / carbonyls (6.9 Å between acceptor sides) even-nb ring: 1,7-distance odd-nb ring: 1,6-distance Goeke A.; Sulfur reports 2002, 23, 3, 243

52 52 VIII. Sulfur in perfumes Sweet scents - sweet, caramel-like odor - generally cyclic dicarbonyl molecule - planar enol-carbonyl acts as a H-donor/H-acceptor pair of 3 Å distance at the olfactory receptor site Maltol Bark of larch trees Roasted barley Pines, wines No significant change Furaneol ® Only minor changes → Structure of bifunctional unit important (not its chemical character: O vs S) Goeke A.; Sulfur reports 2002, 23, 3, 243

53 53 Thank you for your attention!


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