THE PROBLEMS OF SULPHUR
CONTENTS ASYMMETRIC SYNTHESIS OF CHIRAL SULFOXIDES CHIRAL SULFOXIDES INTRODUCTION THE MAIN ROUTES TO CHIRAL SULFOXIDES USE OF CHIRAL SULFUR PRECURSORS SUL?NATES (ANDERSEN METHOD) DIASTEREOSELECTIVE FORMATION OF SUL?NATES SUL?NATES FROM SUL?TES SUL?NAMIDES CATALYTIC ENANTIOSELECTIVE SUL?DE OXIDATION TITANIUM COMPLEXES DIESTERS OF TARTARIC ACID C2-SYMMETRIC 1,2-DIOLS AS LIGANDS BINAPHTHOL AND DERIVATIVES C3-SYMMETRIC TRIETHANOLAMINE LIGANDS TI (SALEN) CATALYSTS MANGANESE COMPLEXES VANADIUM COMPLEXES MOLYBDENUM COMPLEXES IRON COMPLEXES MISCELLANEOUS CATALYTIC ARYLATION OF SULFENATE ANIONS ENANTIOSELECTIVE OXIDATION OF SUL?DES SUMMARY REFERENCES ASYMMETRIC SYNTHESIS OF OPTICALLY ACTIVE SUL?NIC ACID ESTERS ENANTIOMERIC SUL?NIC ACID ESTERS DIASTEREOMERIC SUL?NIC ACID ESTERS ASYMMETRIC TRANSFORMATIONS MEDIATED BY SUL?NYL GROUPS NUCLEOPHILIC ADDITIONS TO CBO AND CBN BONDS MEDIATED BY A-SUL?NYL GROUPS B-KETOSULFOXIDES REDUCTION REACTIONS ALKYLATION REACTIONS ALDOL REACTION WITH B-KETOSULFOXIDES ACTING AS ELECTROPHILES HYDROCYANATION REACTIONS B-IMINO(ENAMINO)SULFOXIDES CONJUGATE ADDITIONS TO A,B-UNSATURATED SULFOXIDES NUCLEOPHILIC ADDITIONS (E) AND (Z)-2-SUBSTITUTED VINYL SULFOXIDES 1-SUBSTITUTED VINYL SULFOXIDES TANDEM REACTIONS RADICAL CONJUGATE ADDITIONS AND OTHER REACTIONS CYCLOADDITIONS ASYMMETRIC DIELS–ALDER REACTIONS SUL?NYL DIENOPHILES SUL?NYL DIENES ASYMMETRIC HETERO DIELS–ALDER REACTIONS ASYMMETRIC 1,3-DIPOLAR CYCLOADDITIONS REACTIONS WITH NITRONES REACTIONS WITH AZOMETHINE YLIDES REACTIONS WITH NITRILE OXIDES REACTIONS WITH DIAZOALKANES REACTIONS WITH OTHER DIPOLES OTHER ASYMMETRIC CYCLOADDITIONS ASYMMETRIC PROCESSES STEREOCONTROLLED BY REMOTE SULFOXIDES NUCLEOPHILIC PROCESSES REACTIONS WITH SUL?NYLATED ELECTROPHILES REACTIONS WITH SUL?NYLATED NUCLEOPHILES ASYMMETRIC PUMMERER REACTION SYNTHESIS AND APPLICATIONS OF CHIRAL DITHIOACETAL DERIVATIVES LITHIATED DITHIANES ALTERNATIVE METHODS OXIDATION METHODS FOR THE CONSTRUCTION OF CHIRAL DITHIOACETAL DERIVATIVES AND APPLICATIONS IN SYNTHESIS APPLICATIONS OF CHIRAL DITHIOACETAL DERIVATIVES IN NATURAL PRODUCT AND BIOLOGICALLY ACTIVE COMPOUND SYNTHESIS SYNTHESIS AND USE OF CHIRAL SULFUR YLIDES REACTIONS OF SULFONIUM YLIDES METHODS OF PREPARATION CONDITIONS FOR STEREOCONTROL AND THEORETICAL INVESTIGATIONS EPOXIDATION REACTION STOICHIOMETRIC USE OF SUL?DES STILBENE OXIDES UNSATURATED EPOXIDES ALIPHATIC EPOXIDES TERMINAL EPOXIDES FUNCTIONAL EPOXIDES CATALYTIC USE OF SUL?DES AZIRIDINATION STOICHIOMETRIC AZIRIDINATION, AND MECHANISM CATALYTIC AZIRIDINATION CYCLOPROPANATION STOICHIOMETRIC CYCLOPROPANATION CATALYTIC CYCLOPROPANATION [2,3]-SIGMATROPIC REARRANGEMENT OTHER REACTIONS CONCLUSIONS SYNTHESIS AND USE OF CHIRAL SULFOXIMINES SYNTHESIS AND STRUCTURAL MODI?CATION APPLICATIONS IN ASYMMETRIC SYNTHESIS USE OF SULFOXIMINES AS CHIRAL AUXILIARIES USE OF SULFOXIMINES AS CHIRAL LIGANDS SYNTHESIS AND USE OF CHIRAL SUL?NAMIDES SYNTHESIS OF CHIRAL SUL?NAMIDES AND CHIRAL SUL?NYLIMINES BACKGROUND SYNTHESIS OF CHIRAL SUL?NAMIDES SYNTHESIS OF CHIRAL SUL?NYLIMINES USE OF CHIRAL SUL?NAMIDES USE AS CHIRAL SUL?NYL AUXILIARIES SYNTHESIS OF CHIRAL AMINES SYNTHESIS OF AZIRIDINES USE OF CHIRAL SUL?NAMIDES AS LIGANDS IN CATALYTIC ASYMMETRIC REACTIONS ASYMMETRIC DIELS–ALDER REACTION ASYMMETRIC ALLYLIC ALKYLATION REACTION ASYMMETRIC HYDROGENATION OF OLE?NS APPLICATION OF CHIRAL SUL?NAMIDES IN THE SYNTHESIS OF BIOLOGICALLY ACTIVE MOLECULES TOTAL SYNTHESIS OF (6R,7S)-7-AMINO-7,8-DIHYDRO-A-BISABOLENE ASYMMETRIC SYNTHESIS OF ()-PATEAMINE SYNTHESIS OF POLYOXAMIC ACID LACTONE SYNTHESIS OF SINGLE ENANTIOMERS OF SIBUTRAMINE AND CETIRIZINE ASYMMETRIC CATALYSIS USING SULFOXIDES AS LIGANDS SOME CONSIDERATIONS ON THE COORDINATION OF SULFOXIDES SULFOXIDES AS LIGANDS IN METAL-CATALYZED ASYMMETRIC CATALYSIS CATALYTIC HYDROGENATIONS CATALYTIC CYCLOADDITIONS ADDITION OF DIETHYLZINC TO BENZALDEHYDE CATALYTIC ALLYLIC SUBSTITUTIONS UTILIZATION OF SULFOXIDES IN OTHER METAL-CATALYZED ASYMMETRIC PROCESSES USE OF SULFOXIDES IN LEWIS ACID–LEWIS BASE BIFUNCTIONAL ASYMMETRIC CATALYSIS USE OF SULFOXIDES AS CHIRAL LIGANDS IN COMBINATION WITH ACHIRAL CATALYSTS USE OF SULFOXIDES AS LIGANDS IN ENANTIOSELECTIVE RADICAL ALLYLATION USE OF SULFOXIDES AS NEUTRAL COORDINATE-ORGANOCATALYSTS SULFONES IN ASYMMETRIC CATALYSIS ALKENYL SULFONES IN ASYMMETRIC CATALYSIS ASYMMETRIC CATALYTIC CONJUGATE ADDITION ASYMMETRIC CATALYTIC CONJUGATE REDUCTION ASYMMETRIC CATALYTIC RADICAL ADDITION ASYMMETRIC CATALYTIC CYCLOADDITIONS ASYMMETRIC CATALYTIC DIHYDROXYLATION AND EPOXIDATION REACTIONS KETOSULFONES ASYMMETRIC REDUCTION OF KETOSULFONES DIELS–ALDER REACTIONS MICHAEL–ALDOL REACTIONS A-DIAZO-B-KETOSULFONES MISCELLANEOUS: OTHER SUBSTITUTED SULFONES ASYMMETRIC REACTION OF A-SULFENYL CARBANIONS ASYMMETRIC REACTIONS OF A-SULFENYL CARBANIONS RACEMIZATION MECHANISM AND CON?GURATIONAL STABILITY OF A-SULFENYL CARBANIONS DIASTEREOSELECTIVE REACTION OF A-SULFENYL CARBANIONS ENANTIOSELECTIVE REACTION OF A-SULFENYL CARBANIONS REACTION PATHWAY OF ENANTIOSELECTIVE REACTION OF A-SULFENYL CARBANIONS ENANTIOSELECTIVE REACTIONS OF A-SULFENYL CARBANIONS ENANTIOSELECTIVE REACTIONS OF A-LITHIATED DITHIOACETALS STEREOSELECTIVE REACTIONS WITH A-SUL?NYL CARBANIONS STEREOCHEMISTRY OF A-SUL?NYL CARBANIONS ALKYLATION OF A-SUL?NYL CARBANIONS CONJUGATED ADDITIONS WITH A-SUL?NYL CARBANIONS ADDITIONS OF A-SUL?NYL CARBANIONS TO CARBONYL COMPOUNDS ADDITIONS OF A-SUL?NYL CARBANIONS TO IMINES AND RELATED COMPOUNDS ASYMMETRIC REACTIONS OF A-SULFONYL CARBANIONS CON?GURATIONALLY STABLE A-SULFONYL CARBANIONS CON?GURATIONALLY LABILE A-SULFONYL CARBANIONS CON?GURATIONALLY LABILE A-SULFONYL CARBANIONS WITH AN ADDITIONAL STEREOGENIC CENTER COMPUTATIONAL STUDIES ON ASYMMETRIC REACTIONS WITH SULFUR REAGENTS DIRECTING E?ECT OF CHIRAL SULFUR SUBSTITUENTS SULFUR CENTERS IN CHIRAL INTERMEDIATES SYNTHESIS OF CHIRAL SULFOXIDES FROM PROCHIRAL SUL?DES SYNTHESIS OF CHIRAL SULFOXIDES FROM RACEMIC PRECURSORS OTHER SYSTEMS INVOLVING CHIRAL SULFUR CENTERS CONCLUSIONS AND PERSPECTIVES INTRODUCTION THE ?RST EXAMPLE OF AN OPTICALLY ACTIVE SULFOXIDE WAS DESCRIBED IN 1926 [1] THIS DISCOVERY WAS HELPFUL FOR DISCUSSIONS REGARDING THE NATURE OF THE SAO BOND AND THE NON-PLANARITY OF SULFUR LATER, CHIRAL SULFOXIDES SLOWLY EMERGED AS A CLASS OF COMPOUNDS OF INTEREST IN ASYMMETRIC SYNTHESIS (FOR REVIEWS, SEE REFS [2–7]) ENANTIOPURE SULFOXIDES ALSO BECAME IMPORTANT IN THE PHARMACEUTICAL INDUSTRY, DUE MAINLY TO THEIR BIOLOGICAL PROPERTIES AS A RESULT, MANY TYPES OF PHARMACEU- TICAL AGENTS BECAME OF SPECIAL INTEREST, MOST NOTABLY ONE CLASS OF ANTI-ULCER DRUGS METHODS FOR THE E?CIENT PREPARATION OF CHIRAL SULFOXIDES ARE ALSO OF PARTICULAR INTEREST [8] HENCE, THIS CHAPTER WILL FOCUS ON APPROACHES BASED ON THE ASYMMET- RIC SYNTHESIS OF CHIRAL SULFOXIDES IN A BROAD SENSE, WHERE A CHIRAL AUXILIARY IS USED IN EITHER A STOICHIOMETRIC OR CATALYTIC MANNER AND, PREFERENTIALLY, IS ALSO REUSABLE THE MAIN ROUTES TO CHIRAL SULFOXIDES THE MAIN ROUTES TO CHIRAL SULFOXIDES ARE DEPICTED IN SCHEME 1 1 THE RESOLUTION OF A RACEMIC MIXTURE (ROUTE I) WAS THE ?RST METHOD USED TO PRODUCE CHIRAL SULF- OXIDES, BY EITHER A CHEMICAL APPROACH OR AN ENZYMATIC REACTION SINCE THE 1960S, THE TRANSFORMATION OF A DIASTEREOCHEMICALLY PURE SUL?NATE HAS BEEN A VERY USEFUL METHOD BY WHICH TO OBTAIN SULFOXIDES WITH HIGH ENANTIOMERIC EXCESS (EE) VALUES (ROUTE II) THE ENANTIOSELECTIVE OXIDATION OF PROCHIRAL SUL?DES BY ENZYMATIC OR NON-ENZYMATIC METHODS REPRESENTS A RELATIVELY DIRECT WAY (ROUTE III) TO PREPARE ENANTIOENRICHED SULFOXIDES ANOTHER PREPARATIVE METHOD (ROUTE IV) IS TO MODIFY THE STRUCTURE OF SOME CHIRAL SULFOXIDES WITHOUT ANY LOSS OF STEREOCHEMISTRY AT THE SULFUR ATOM IN THIS CHAPTER, ATTENTION WILL BE FOCUSED ON NON-ENZYMATIC ASYMMETRIC SYNTHESES OF SULFOXIDES, EXCLUDING THE RESOLUTION PROCESSES TWO CLASSES OF REACTIONS WILL BE SUBSEQUENTLY PRESENTED – THE STOICHIOMETRIC ASYMMETRIC SYNTHESES, AND THE CATA- LYTIC ASYMMETRIC SYNTHESES SCHEME 1 1 THE MAIN ROUTES TO CHIRAL SULFOXIDES SUL?NATES (ANDERSEN METHOD) CHIRAL SUL?NATES ARE EXCELLENT PRECURSORS OF CHIRAL SULFOXIDES, AND THIS APPROACH WAS PIONEERED BY ANDERSEN IN 1962, USING ONE DIASTEREOMER OF MENTHYL P- TOLYLSUL?NATE PREPARED FROM ()-MENTHOL [9, 10] THE REACTION WAS OF PREPARATIVE INTEREST, AND PROVIDED SULFOXIDES OF VERY HIGH EE-VALUES THE INVERSION OF CON- ?GURATION FOR THE SUBSTITUTION REACTION WAS ?RMLY ESTABLISHED [11, 12] THE NOW SO-CALLED ANDERSEN METHOD IS ILLUSTRATED SCHEMATICALLY IN SCHEME 1 2 FOR THE SYN- THESIS OF THE P-TOLYL SULFOXIDES 2 HERE, THERE ARE TWO IMPORTANT ISSUES: (1) THE NEED TO PREPARE THE MENTHYL P-TOLYLSUL?NATES 1 FROM ()-MENTHOL; AND (2) TO SEP- ARATE THE TWO EPIMERS AT SULFUR THE P-TOLYLSUL?NYL CHLORIDE (1) WAS PREPARED IN SITU BY THE REDUCTION OF P-TOLYLSULFONYL CHLORIDE ACCORDING TO A KNOWN PROCEDURE [13] SUBSEQUENT SEPARATION OF THE TWO EPIMERS COULD BE ACHIEVED BY CRYSTALLIZA- TION, AS (SS)-2 IS CRYSTALLINE AND (RS)-2 IS OILY VERY SOON, THE ANDERSEN METHOD BECAME THE PREFERRED APPROACH WHEN PREPARING ENANTIOPURE SULFOXIDES OF KNOWN ABSOLUTE CON?GURATION THE LARGE MAJORITY OF EXAMPLES USED AS THE STARTING MATE- RIAL SUL?NATE (SS)-2 DUE TO THE EASE OF ITS PREPARATION AN IMPORTANT IMPROVEMENT (GIVING 90% YIELD) OF THE PREPARATION OF ()-MENTHYL P-TOLYLSUL?NATE [(SS)-2] WAS INTRODUCED BY MIOSKOWSKI AND SOLLADIE´ IN 1980 [14] THESE AUTHORS COMBINED THE CRYSTALLIZATION STEP IN ACETONE WITH AN IN-SITU EPIMERIZATION BY A CATALYTIC AMOUNT SCHEME 1 2 THE ANDERSEN METHOD FOR THE PREPARATION OF CHIRAL SULFOXIDES 1 2 USE OF CHIRAL SULFUR PRECURSORS AND CHIRAL ALCOHOL) (SCHEME 1 3) SOME KINETIC DIASTEREOSELECTIVITY (UP TO 10 : 1) HAS BEEN OBSERVED BY WHITESELL AND COLLEAGUES IN SUL?NATE FORMATION (7 AND 8) FROM 2-PHENYLCYCLOHEXANOL 6 (SCHEME 1 3) [20A,B] ONE IMPROVEMENT IN THE SYN- THESIS OF SUL?NATES WAS THE INTERMEDIATE FORMATION OF CHLOROSUL?TE ESTERS BY THE ACTION OF THIONYL CHLORIDE ON TRANS-PHENYLCYCLOHEXANOL 6 (SCHEME 1 3) [20B] THE MIXTURE OF DIASTEREOMERIC CHLOROSUL?TES WAS THEN TREATED WITH VARIOUS DI- ALKYLZINCS OVER A RANGE OF CONDITIONS, AND AS A CONSEQUENCE SUL?NATE ESTER 7 WAS OBTAINED WITH UP TO 97% YIELD AND 92% DIASTEREOMERIC EXCESS (DE) THE AUTHORS ASSUMED A DYNAMIC KINETIC RESOLUTION PROCESS WHERE THE CHLOROSUL?NATES WERE IN TABLE 1 1 SYNTHESIS OF SOME CRYSTALLINE MENTHYL SUL?NATES ENTRY R REFERENCE 1-NAPHTHYL 1-(2-NAPHTHYL) 1-(2-OME-NAPHTHYL) 4-BROMOPHENYL