Comprehensive Organic Functional Group Transformations, Volume4 (Synthesis: Carbon with Two Heteroatoms, Each Attached by a Single Bond)

1217 Pages·2003·12.12 MB·English

by  Alan R. Katritzky

Comprehensive Organic Functional
Group Transformations, Volume 4
Elsevier, 2003

Editors-in-Chief: Alan R. Katritzky, Otho Meth-Cohn, and Charles W. Rees

Synthesis: Carbon with Two Heteroatoms, Each Attached by a
Single Bond

Part I: Tetracoordinated Carbon Functions Bearing Two Heteroatoms, R CXX′
2

4.01 Dihalo Alkanes, R C(Hal) , Pages 1-40, Robert A. Hill
2 2

4.02 Functions Incorporating a Halogen and a Chalcogen, Pages 41-93,
Niall W. A. Geraghty
4.03 Functions Incorporating a Halogen and Another Heteroatom Group Othe
Than a Chalcogen, Pages 95-157, Alex C. Campbell and David R. Jaap
4.04 Functions Bearing Two Oxygens, R1 C(OR2) , Pages 159-214, David
2 2
T. Macpherson and Harshad K. Rami
4.05 Functions Incorporating Oxygen and Another Chalcogen, Pages 215-241,
Richard H. Wightman
4.06 Functions Incorporating Two Chalcogens Other Than Oxygen, Pages 243-291,
Yannick Vallée and Andrew Bulpin
4.07 Functions Incorporating a Chalcogen and a Group 15 Element, Pages 293-349,
Christopher D. Gabbutt and John D. Hepworth
4.08 Functions Incorporating a Chalcogen and a Silicon, Germanium, Boron or
Metal, Pages 351-402, Max J. Gough and John Steele
4.09 Functions Bearing Two Nitrogens, Pages 403-449, Derek R. Buckle and Ivan
L. Pinto
4.10 Functions Containing a Nitrogen and Another Group 15 Element, Pages
451-504, Frances Heaney
by kmno4
4.11 Functions Incorporating a Nitrogen and a Silicon, Germanium, Boron or Metal,
Pages 505-541, John Steele and Max J. Gough
4.12 Functions Containing One Phosphorus and Either Another Phosphorus or As,
Sb, Bi, Si, Ge, B or a Metal, Pages 543-589, R. Alan Aitken
4.13 Functions Containing at Least One As, Sb or Bi with or without a Metalloid
(Si or Ge) or a Metal, Pages 591-600, William M. Horspool
4.14 Functions Containing at Least One Metalloid (Si, Ge or B) Together with
Another Metalloid or Metal, Pages 601-665, Christopher G. Barber
4.15 Functions Containing Two Atoms of the Same Metallic Element, Pages
667-703, William J. Kerr and Peter L. Pauson
4.16 Functions Containing Two Atoms of Different Metallic Elements, Pages
705-727, William J. Kerr and Peter L. Pauson

Part II: Tricoordinated Carbon Functions Bearing Two Heteroatoms, R C=CXX′
2

4.17 Functions Incorporating Two Halogens or a Halogen and a Chalcogen, Pages
729-788, Peter D. Kennewell, Robert Westwood and Nicholas J. Westwood
4.18 Functions Incorporating a Halogen or Another Group other than a Halogen
or a Chalcogen, Pages 789-822, David I. Smith
4.19 Functions Bearing Two Chalcogens, Pages 823-877, Gary N. Sheldrake

4.20 Functions Containing a Chalcogen and Any Group Other Than a Halogen or
a Chalcogen, Pages 879-965, Peter D. Kennewell, Robert Westwood and
Nicholas J. Westwood
4.21 Functions Containing at Least One Nitrogen and No Halogen or Chalcogen,
Pages 967-1020, Graham L. Patrick
4.22 Functions Containing at Least One Phosphorus, Arsenic, Antimony
or Bismuth and No Halogen, Chalcogen or Nitrogen, Pages 1021-1042,
John M. Berge
4.23 Functions Containing at Least One Metalloid (Si, Ge or B) and No Halogen,
Chalcogen or Group 15 Element; also Functions Containing Two Metals,
Pages 1043-1070, Richard A. B. Webster

Part III: Tri- and Dicoordinated Ions, Radicals and Carbenes Bearing Two Heteroatoms
(RC+X1X2, RC−X1X2, RC·X1X2, :CX1X2)

4.24 Tri- and Dicoordinated Ions, Radicals and Carbenes Bearing Two Heteroatoms
(RC+X1X2, RC−X1X2, RC · X1X2, :CX1X2), Pages 1071-1083, William M. Horspool
4.25 References to Volume 4, Pages 1085-1229

by kmno4
4.01
Dihalo Alkanes, R C(Hal)
2 2
ROBERT A. HILL
UniversityofGlasgow,UK
3[90[0 GENERALMETHODS 1
3[90[1 DIFLUOROALKANES*RCF 1
1 1
3[90[1[0 Di~uoroAlkanesfromAlkanes 1
3[90[1[1 Di~uoroAlkanesfromDihaloAlkanes 2
3[90[1[2 Di~uoroAlkanesfromTrihaloAlkanes 4
3[90[1[3 Di~uoroAlkanesfromAlkenes 4
3[90[1[4 Di~uoroAlkanesfromAlkynes 5
3[90[1[5 Di~uoroAlkanesfromDi~uorocarbene 6
3[90[1[6 Di~uoroAlkanesfromAldehydesandKetones 7
3[90[1[7 Di~uoroAlkanesfromImines 09
3[90[2 DICHLOROALKANES*RCCl 00
1 1
3[90[2[0 DichloroAlkanesfromAlkanes 00
3[90[2[1 DichloroAlkanesfromDihaloAlkanes 02
3[90[2[2 DichloroAlkanesfromTrihaloAlkanes 02
3[90[2[3 DichloroAlkanesfromAlkenes 03
3[90[2[4 DichloroAlkanesfromAlkynes 04
3[90[2[5 DichloroAlkanesfromDichlorocarbene 05
3[90[2[6 DichloroAlkanesfromAldehydesandKetones 07
3[90[2[7 DichloroAlkanesfromImines 08
3[90[3 DIBROMOALKANES*RCBr 08
1 1
3[90[3[0 DibromoAlkanesfromAlkanes 08
3[90[3[1 DibromoAlkanesfromDihaloAlkanes 11
3[90[3[2 DibromoAlkanesfromTrihaloAlkanes 12
3[90[3[3 DibromoAlkanesfromAlkenes 12
3[90[3[4 DibromoAlkanesfromAlkynes 13
3[90[3[5 DibromoAlkanesfromDibromocarbene 13
3[90[3[6 DibromoAlkanesfromAldehydesandKetones 14
3[90[3[7 DibromoAlkanesfromImines 16
3[90[3[8 DibromoAlkanesfromCarboxylicAcids 16
3[90[4 DIIODOALKANES*RCI 17
1 1
3[90[4[0 DiiodoAlkanesfromAlkanes 17
3[90[4[1 DiiodoAlkanesfromHaloAlkanes 17
3[90[4[2 DiiodoAlkanesfromAlkynes 18
3[90[4[3 DiiodoAlkanesfromDiiodocarbene 18
3[90[4[4 DiiodoAlkanesfromImines 18
3[90[5 FLUOROHALOALKANES*RCFHal 29
1
3[90[5[0 Chloro~uoroAlkanes*RCClF 29
1
3[90[5[0[0 Chloro~uoroalkanesfromhaloalkanes 29
3[90[5[0[1 Chloro~uoroalkanesfromhaloalkenes 29
3[90[5[0[2 Chloro~uoroalkanesfromchloro~uorocarbene 21
3[90[5[0[3 Chloro~uoroalkanesfromimines 21
3[90[5[0[4 Chloro~uoroalkanesfromcarboxylicacids 22
3[90[5[1 Bromo~uoroAlkanes*RCBrF 22
1
3[90[5[1[0 Bromo~uoroalkanesfromhaloalkanes 22
3[90[5[1[1 Bromo~uoroalkanesfromhaloalkenes 23
0
1 DihaloAlkanes
3[90[5[1[2 Bromo~uoroalkanesfrombromo~uorocarbene 24
3[90[5[1[3 Bromo~uoroalkanesfromcarboxylicacids 24
3[90[5[2 FluoroiodoAlkanes*RCFI 25
1
3[90[5[2[0 Fluoroiodoalkanesfromhaloalkanes 25
3[90[5[2[1 Fluoroiodoalkanesfromhaloalkenes 25
3[90[5[2[2 Fluoroiodoalkanesfrom~uoroiodocarbene 25
3[90[5[2[3 Fluoroiodoalkanesfromcarboxylicacids 26
3[90[6 CHLOROHALOALKANES*RCClHal"notF# 26
1
3[90[6[0 BromochloroAlkanes*RCBrCl 26
1
3[90[6[0[0 Bromochloroalkanesfromhaloalkanes 26
3[90[6[0[1 Bromochloroalkanesfromhaloalkenes 27
3[90[6[0[2 Bromochloroalkanesfrombromochlorocarbene 27
3[90[6[0[3 Bromochloroalkanesfromketones 27
3[90[6[0[4 Bromochloroalkanesfromcarboxylicacids 27
3[90[6[1 Chloroiodoalkanes*RCClI 28
1
3[90[6[1[0 Chloroiodoalkanesfromhaloalkanes 28
3[90[6[1[1 Chloroiodoalkanesfromhaloalkenes 28
3[90[6[1[2 Chloroiodoalkanesfromketones 39
3[90[6[1[3 Chloroiodoalkanesfromcarboxylicacids 39
3[90[7 BROMOIODOALKANES*RCBrI 39
1
3[90[0 GENERALMETHODS
There are many general methods for the preparation of ‘em!di~uoro\ ‘em!dichloro and ‘em!
dibromoalkanes[Thesearegivenindetailinthefollowingsections[Directhalogenationofalkanes
is of limited use as there is generally little control of the site of halogenation[ The method can be
useful\ however\ when there is some control such as halogenation of benzylic positions or a to a
carbonylgroup[Replacementofonehalogenforanothercanbeusefulfordiiodoandmixed‘em!
dihalo alkanes\ but it is often very di.cult to control the degree of exchange[ One of the major
problemsinthegenerationof‘em!dihaloalkanesbythismethodisthepossibilityofeliminationof
hydrogenhalideunderthereactionconditions[Thisisaparticularproblemfordihaloalkaneswhere
oneofthehalidesisbromineoriodine[
Addition of hydrogen halides or halogens to halo alkenes has been used extensively for the
production of dihalo alkanes[ Radical addition of hydrogen halides often leads to 0\1!dihalo
compoundsandcaremustbetakentoreducethepossibilityofradicalformation[Otherproblems
ofdirectionofadditionoccurwheninterhalogencompoundsareaddedacrosshaloalkenes^mixtures
ofproductsareoftenobtained[
Dihalocarbenes have been used extensively in addition reactions to double bonds to form
dihalocyclopropanederivatives[Therearemanymethodsforthegenerationofcarbenesore}ectinga
carbenetransfer\particularlyfordi~uoro!\dichloro!anddibromocarbene[Theotherdihalocarbenes
havebeenstudiedlessextensively[
Theconversionofanaldehydeorketoneintoadihaloalkaneworkswellwith~uoroandchloro
alkanes\butbromoandiodoalkanesareeasilyhydrolysedbacktothealdehydeandketone[Many
preparationsofdibromoanddiiodoalkanesresultincarbonylcompoundsassideproducts[
3[90[1 DIFLUOROALKANES*R CF
1 1
Thepreparationof‘em!di~uoroalkanesisincludedinageneralreviewbyHenneonthesynthesis
ofaliphatic~uorinecompounds(cid:2)33OR"1#38(cid:3)[
3[90[1[0 Di~uoroAlkanesfromAlkanes
Direct ~uorination of saturated compounds has been used since 0899 to replace hydrogen by
~uorine (cid:2)33OR"1#38(cid:3)[ However\ the reaction is not easy to control^ most organic compounds react
violentlywith~uorine[Thereactionofelementalcarbonwith~uorinehasbeenreportedtogivea
mixture of products from which per~uoropropane\ per~uorobutane and per~uoropentane have
been isolated (cid:2)26JA0396(cid:3)[ This method is clearly not of general application[ More!controlled ~uo!
rination of ethane using ~uorine diluted with nitrogen yielded partially ~uorinated ethanes from
Di~uoroAlkanes 2
which CHF CHF and CHF CH F could be isolated (cid:2)39JA0060(cid:3)[ Electrochemical ~uorination of
1 1 1 1
ethanewithasolutioninhydrogen~uorideisamorecontrollablemethodbutagainmixtureswere
obtained\ however\ CH CHF could be obtained in usable amounts (cid:2)55BCJ108(cid:3)[ Cobalt tri~uoride
2 1
is a useful reagent for the per~uorination of unsaturated compounds[ For example\ cyclopentane
can be per~uorinated "Equation "0##\ however the substitution of the last few hydrogens in a
compoundrequireshighertemperatures(cid:2)40JA3130(cid:3)[Per~uorocyclohexanehasbeenpreparedfrom
benzene with ~uorine and a catalyst "Equation "1## (cid:2)49JCS1578(cid:3)[ Gold was found to be the best
catalyst[Per~uorocyclohexanehasalsobeenmadefrommethylbenzoatebytheactionofpotassium
tetra~uorocobaltateathightemperatures"Equation"2##(cid:2)62JFC"2#218(cid:3)[Activemethylenecompounds
havebeenreportedtobe~uorinatede.cientlywithtwoequivalentsofsodiumethoxideinethanol
followedbyperchloryl~uoride"Equations"3#(cid:1)"5##(cid:2)47JA5422(cid:3)^however\alaterreportsuggeststhat
thereactionisquitecomplex(cid:2)55JOC805(cid:3)[
F F
F F
CoF3, 325 °C
F F (1)
F F
F F
F F
F F
F2, Au F F
(2)
40% F F
F F
F F
F F
F F
COMe
2 KCoF4, 300 °C F F
(3)
25% F F
F F
F F
O
O COEt EtONa, EtOH, FClO3 CO2Et (4)
2 59%
F F
CO2Et EtONa, EtOH, FClO3 F CO2Et
(5)
CO2Et 84% F CO2Et
O O
O O EtONa, EtOH, FClO3
(6)
77%
F F
3[90[1[1 Di~uoroAlkanesfromDihaloAlkanes
The substitution of halide in dihalo alkanes using metal ~uorides is of general use for the
preparation of di~uoro alkanes as the corresponding dichloro and dibromo alkanes are generally
more accessible[ The ease of substitution is I(cid:29)Br(cid:29)Cl^ the substitution of chlorine frequently
requires very high temperatures[ Potassium ~uoride will displace the chlorine in the relatively
reactivea!ketoalkylchlorides"forexampleEquation"6##(cid:2)75JA6628(cid:3)\whereasthechlorineofN\N!
diethylchloro~uoroacetamide can only be displaced at high temperatures "Equation "7##
(cid:2)66CCC1426(cid:3)[ Substitution of unreactive chlorines such as in dichloromethane requires harsher
conditions\forexampleameltofpotassiumhydrogendi~uoride\KHF "Equation"8##(cid:2)55AG"E#203(cid:3)[
1
KHF hasalsobeenusedtoprepare0\0!di~uoroacetonefrom0\0!dichloroacetone"Equation"09##
1
(cid:2)60JCS"C#168(cid:3)[Mercuric~uoridehasbeenextensivelyusedforthepreparationof~uoroalkanesby
displacement (cid:2)33OR"1#38(cid:3)[ Bromine is substituted at low temperature with good yields "Equation
"00##whereaschlorinerequireshightemperaturesandresultsinlowyields"Equation"01##(cid:2)25JA778(cid:3)[
3 DihaloAlkanes
O O
KF
Cl F
Ph Ph (7)
28%
Cl F
O O
Cl KF, 140 °C F
NEt NEt (8)
2 2
75%
F F
Cl Cl KHF2 F F (9)
82%
O O
Cl KHF2 F
(10)
50%
Cl F
Br F
HgF2, 0 °C
(11)
Br F
Cl F
HgF2, 140 °C
(12)
Cl Cl
Cl 10% F
Dibromo alkanes are generally smoothly substituted by mercuric ~uoride "Equation "02## but
2\2!dibromobutan!1!one gives side reactions including the production of diacetyl "Equation "03##
(cid:2)66JOC2416(cid:3)[ Silver ~uoride has been used in these reactions^ however\ it is di.cult to prepare in
anhydrous form and it forms insoluble\ complex silver halides (cid:2)33OR"1#38(cid:3)[ Antimony tri~uoride
with a catalytic amount of bromine converts dichloro"diphenyl#methane into di~uoro!
"diphenyl#methaneinhighyield"Equation"04##(cid:2)27JA753(cid:3)[Antimonypenta~uorideisverye}ective
at substituting alkyl bromides "Equation "05## and alkyl chlorides "Equation "06## but it does not
exchangevinylhalides(cid:2)55JA1370(cid:3)[Amixtureofantimonytri~uoride\antimonypentachlorideand
hydrogenchloride hasbeenusedto convert1\1!dichlorobutaneinto1\1!di~uorobutane "Equation
"07##butmanysidereactionsoccurred(cid:2)68JFC"02#214(cid:3)
O O
HgF2
(13)
Ph Ph
89%
Br Br F F
O O
HgF2
(14)
Br Br O
Cl Cl SbF3, Br2 (cat.), 140 °C F F
(15)
Ph Ph Ph Ph
Br Br F F
SbF5, 109 °C
(16)
51%
Br Br Br Br
Cl Cl F F
SbF5, 110 °C
(17)
Cl Cl Cl Cl
Cl Cl SbF3, SbCl5, HCl F F
(18)
Di~uoroAlkanes 4
3[90[1[2 Di~uoroAlkanesfromTrihaloAlkanes
Reduction of the bromodi~uoromethyl group with sodium borohydride in DMSO seems an
attractivemethodofpreparationofcompoundscontainingthedi~uoromethylgroupaslongasthe
startingmaterialisreadilyavailableas"Equation"08##(cid:2)80JOC3211(cid:3)[
F F
F
NaBH4, DMSO
Br F (19)
51%
Br
3[90[1[3 Di~uoroAlkanesfromAlkenes
Addition of an acid to a 0\0!di~uoro alkene will lead to a di~uoromethyl group[ The high
electronegativity of ~uorine ensures that hydrogen adds to the carbon bearing the ~uorines[ Thus
hydrogen bromide "Equation "19## and hydrogen iodide "Equation "10## add e.ciently to 0\0!
di~uoroethene(cid:2)45JCS50(cid:3)[Methanolwilladdacrosstetra~uoroetheneinthepresenceofacatalytic
amount of sodium methoxide "Equation "11## (cid:2)40JA0218(cid:3)[ The addition to the electron!de_cient
tetra~uoroethene is initially by nucleophilic attack[ Cyanide will add to chlorotri~uoroethene to
give\ after acid hydrolysis\ 2!chloro!1\1\2!tri~uoropropanoic acid "Equation "12## (cid:2)59OSC"4#128(cid:3)[
Tetra~uoroethenecanbealkylatedusingaluminumtrichlorideasacatalyst\forexample\dichloro!
~uoromethanecanbee}ectivelyaddedacrossthedoublebondas"Equation"13##(cid:2)60CCC0756(cid:3)[
F F
HBr
Br
(20)
F 100% F
F F
HI
I
(21)
F 100% F
F F
MeOH, MeONa (cat.), 35 °C, 5 h F
F F (22)
F OMe
81%
F F
F i, KCN F
ii, H+ F
Cl Cl
(23)
F 76–79% CO2H
F F
F
F
F CHFCl2, AlCl3, 10 °C, 5 h F
F Cl (24)
58% FC
3
F
Cl
The(cid:2)1(cid:27)1(cid:3)adductsof~uoroalkenescanbepreparedathightemperatures\probablyinvolvinga
radicalmechanism[Tetra~uoroethenecanbedimerisedat599>Ctogiveper~uorobutane"Equation
"14##^ temperatures above 599>C give various side reactions including polymerisation (cid:2)42JCS1972(cid:3)[
Mixed cycloaddition reactions such as tetra~uoroethene with ethene as in "Equation "15##\ with
butadiene "Equation "16## and with acrylonitrile "Equation "17## are possible\ as they occur much
morereadilythanthedimerisationoftetra~uoroethene(cid:2)38JA389(cid:3)[Tetra~uoroethenewillalsoadd
to acetylene to give 2\2\3\3!tetra~uorocyclobutene "Equation "18## (cid:2)50JA271(cid:3)[ A variety of other
~uorinated ethenes will cyclodimerise "Equations "29# and "20## at lower temperatures than tetra!
~uoroethene (cid:2)36JA168(cid:3)[ Intramolecular (cid:2)1(cid:27)1(cid:3) cycloaddition of 0\0!di~uorobutadiene takes place
underUVirradiation"Equation"21##(cid:2)76JOC0761(cid:3)[
5 DihaloAlkanes
F F
F
600 °C F F
F
F (25)
42% F F
F
F F
F
F
150 °C, 8 h F
F F + H2C CH2 (26)
F
40%
F
F
F
F
125 °C, 8 h F
F F + (27)
F
90%
F
F
F
F
F F + CN 150 °C, 8 h FF (28)
84%
F CN
F
F
F
F F + H H 225 °C, 12 h F (29)
F
35%
F
F
F F
F
200 °C, 12 h F F
Cl
(30)
F
Cl Cl
80%
Cl
Cl Cl
F F
F
200 °C, 8 h F F
Cl
(31)
F
Cl Cl
80%
F
F F
F hn , 4 days F
F (32)
F
3[90[1[4 Di~uoroAlkanesfromAlkynes
Theadditionoftwoequivalentsofhydrogen~uorideacrossatriplebondisageneralmethodof
preparingdi~uoroalkanes"Equation"22##(cid:2)36JA170(cid:3)[Fluorinationofalkynesby~uorineinmeth!
anolleadstotheformationofa‘em!di~uorodimethylacetal"Equation"23##(cid:2)75JA6628(cid:3)[
HF F
Cl F (33)
Cl
50%
OMe
MeO
F2, MeOH F
Ph Ph (34)
F
Di~uoroAlkanes 6
3[90[1[5 Di~uoroAlkanesfromDi~uorocarbene
Thegenerationofdi~uorocarbenehasbeenextensivelyreviewed(cid:2)52OR"02#44\B!58MI390!90\B!60MI
390!90\66FCR008\B!74MI390!90(cid:3)[ Di~uorocarbene transfer is most commonly achieved by decompo!
sition of a tri~uoromethyl(cid:1)metal complex[ Pyrolysis of trimethyltri~uoromethyl tin generates
per~uorocyclopropane "Equation "24##\ formed by di~uorocarbene dimerisation to tetra!
~uoroethene\ which undergoes a di~uorocarbene addition (cid:2)59JA0777(cid:3)[ Pyrolysis of potassium
tri~uoromethyl~uoroborate also gives per~uorocyclopropane together with per~uorocyclobutane
"Equation "25## (cid:2)59JA4187(cid:3)[ The complex of bis"tri~uoromethyl#cadmium and DIGLYME reacts
with acetyl chloride to produce acetyl ~uoride and di~uorocarbene\ which can be trapped with
1\2!dimethylbut!1!ene in high yield "Equation "26## (cid:2)70JA1884(cid:3)[ Metallic lead and dibromo!
di~uoromethane have been used to produce di~uorocarbene and its capture by several alkenes
studied(cid:2)70ZN"B#0264(cid:3)[TetrabutylammoniumbromidewasaddedtoformacomplexwiththePbBr
1
producedinthereaction[Excellentyieldswereachievedwith1\2!dimethylbut!1!ene"Equation"27##
buttheyieldsdecreasewithlesssubstitutedalkenes"Equations"28#and"39##[
F F
150 °C, 20 h
Me3SnCF3 F F (35)
F F
F F F F
300 °C F F
KCF3BF3 F F + (36)
F F
F F
F F
F F
(CF3)2Cd, DIGLYME, AcCl, –27 °C
(37)
70%
F F
CBr2F2, Pb, Bu4NBr
(38)
80–90%
F F
Ph
CBr2F2, Pb, Bu4NBr
Ph (39)
55%
F F
Ph CBr2F2, Pb, Bu4NBr
(40)
17%
Ph
Bromodi~uoromethylphosphonium salts\ prepared in situ\ are good sources of di~uorocarbene[
Treatment with caesium ~uoride formed di~uorocarbene\ which added to 1\2!dimethylbut!1!ene
"Equation"30##(cid:2)62JA7356(cid:3)\whereaspotassium~uoridewasusedlikewisewithbutadiene"Equation
"31## (cid:2)71JA1383(cid:3)[ Di~uorotris"tri~uoromethyl#phosphorane has been used to transfer di~uoro!
carbenetoavarietyofhalogenatedalkenes"Equation"32##(cid:2)69JCS"C#067(cid:3)[
F F
CBr2F2, PPh3, CsF, RT, 24 h
(41)
79%
F F
CBr2F2, PPh3, KF
(42)
55%
7 DihaloAlkanes
F F
F Cl
(CF3)3PF2, 120 °C, 24 h
F Cl (43)
Cl Cl
Cl Cl
Oneofthemostusefulreagentsforgeneratingdi~uorocarbeneisphenyltri~uoromethylmercury
(cid:2)61ACR54(cid:3)^ an example of its use is the addition of di~uorocarbene to benzobarrelene "Equation
"33##(cid:2)68TL0802(cid:3)[Oneoftheearliestmethodsusedtogeneratedi~uorocarbenewaspyrolysisofthe
sodiumchlorodi~uoroacetate(cid:2)59PCS70\53TL0350(cid:3)^ithasbeenusedtoaddtoadoublebond"Equa!
tion"34##(cid:2)62TL0208(cid:3)[Thehinderedbase\sodiumbis"trimethylsilyl#amide\hasbeenusedtogenerate
di~uorocarbene from chlorodi~uoromethane[ The di~uorocarbene reacted with a malonate anion
togiveanadditionproduct"Equation"35##(cid:2)74TL1334(cid:3)[
PhHgCF3
(44)
F
F
O O
O O
F2ClCCO2Na, DIGLYME, reflux
(45)
O F F O
F
COEt
2
COEt
CHClF2, NaN(TMS)2 (3 equiv.) F 2
N COEt (46)
2 N CO Et
2
Ph
Ph
3[90[1[6 Di~uoroAlkanesfromAldehydesandKetones
Sulfurtetra~uoridewasthe_rstreagentusedtoconvertaldehydesandketonesinto‘em!di~uoro
alkanes[ Two excellent reviews cover the use of sulfur tetra~uoride (cid:2)63OR"10#0\74OR"23#208(cid:3)^ a few
exampleswillbegivenheretohighlighttheadvantagesanddisadvantages[Aldehydesandketones
witha!hydrogenatomsneedtobetreatedatlowtemperaturesforlongperiodstopreventdecompo!
sitionasshowninEquations"36#and"37#(cid:2)60JOC707(cid:3)[Aromaticaldehydes"Equation"38##(cid:2)60T834(cid:3)
andhighertemperatures\generally049(cid:1)199>C\givemuchhigheryields[Formaldehyde"intheform
of paraformaldehyde# at a high temperature "049>C# gave only a modest yield "Equation "49##
(cid:2)59JA432(cid:3)[
O F F
SF4, CH2Cl2, 30 °C, 120 h
(47)
39%
O F F
SF4, CH2Cl2, 30 °C, 48 h
(48)
70%
CHO F F
SF4, 150 °C, 6 h
(49)
F
F