Abstract
The reaction between carboxylic acids (RCOOH) and dialkyl dicarbonates [(R1 OCO)2 O], in the presence of a weak Lewis acid such as magnesium chloride and the corresponding alcohol (R1 OH) as the solvent, leads to the esters RCOOR1 in excellent yields. The mechanism involves a double addition of the acid to the dicarbonate, affording a carboxylic anhydride [(RCO)2 O], R1 OH and carbon dioxide. The esters arise from the attack of the alcohols on the anhydrides. Exploiting the lesser reactivity of tert -butyl alcohol in comparison with other alcohols, a clean synthesis of both carboxylic anhydrides and esters has been set up. In the former reaction, an acid/Boc2 O molecular ratio of 2:1 leads to the anhydride in good to excellent yields, depending on the stability of the resulting anhydride to the usual workup conditions. In the latter reaction, stoichiometric mixtures of the acid and Boc2 O are allowed to react with a twofold excess of a primary alcohol, secondary alcohol or phenol (R2 OH) to give the corresponding esters (RCOOR2 ). Purification of the products is particularly easy since all byproducts are volatile or water soluble. A very easy chromatography is required only in the case of nonvolatile alcohols. A broad variety of sensitive functional groups is tolerated on both the acid and the alcohol, in particular a high chemoselectivity is observed. In fact, no transesterification processes occur with the acid-sensitive acetoxy group and methyl esters.
Key words
synthetic methods - anhydrides - esters - Lewis acids - magnesium salts
References
For recent literature, see among others:
1a
Varala R.
Nuvula S.
Adapa SR.
J. Org. Chem.
2006,
71:
8283
1b
Chankeshwara SV.
Chakraborti AK.
Synthesis
2006,
2784
1c
Reddy MS.
Narender M.
Nageswar YVD.
Rao KR.
Synlett
2006,
1110
1d
Heydari A.
Hosseini SE.
Adv. Synth. Catal.
2005,
347:
1929
1e
Bartoli G.
Bosco M.
Locatelli M.
Marcantoni E.
Massaccesi M.
Melchiorre P.
Sambri L.
Synlett
2004,
1794
For recent literature, see among others:
2a
Bartoli G.
Bosco M.
Carlone A.
Locatelli M.
Marcantoni E.
Melchiorre P.
Palazzi P.
Sambri L.
Eur. J. Org. Chem.
2006,
4429
2b
Bartoli G.
Bosco M.
Carlone A.
Dalpozzo R.
Locatelli M.
Melchiorre P.
Palazzi P.
Sambri L.
Synlett
2006,
2104
2c
Chen CT.
Kuo JH.
Pawar VD.
Munot YS.
Weng SS.
Ku CH.
Liu CY.
J. Org. Chem.
2005,
70:
1188
2d
Peri F.
Binassi E.
Manetto A.
Marotta E.
Mazzanti A.
Righi P.
Scardovi N.
Rosini G.
J. Org. Chem.
2004,
69:
1353
2e
Haight AR.
Stoner EJ.
Peterson MJ.
Grover VK.
J. Org. Chem.
2003,
68:
8092
2f
Ouchi H.
Saito Y.
Yamamoto Y.
Takahata H.
Org. Lett.
2002,
4:
585
3a
Parrish JP.
Salvatore RN.
Jung KW.
Tetrahedron
2000,
56:
8207
3b
Shaikh AAG.
Sivaram S.
Chem. Rev.
1996,
96:
951
4 Organic carbonates, for example, find employment as fuel additives, lubricating oils, herbicides, pesticides, plastics and solvents, and for medicinal and biological applications.
5
Greene TW.
Wuts PGM.
Protective Groups in Organic Synthesis
3rd ed.:
Wiley;
New York:
1999.
p.518-525
6 Ref. 5, p 281.
7
Takeda K.
Akiyama A.
Nakamura H.
Takizawa S.
Mizuno Y.
Takayanagi H.
Harigaya Y.
Synthesis
1994,
1063
8
Gooßen L.
Döhring A.
Adv. Synth. Catal.
2003,
345:
943
9
Bartoli G.
Bosco M.
Carlone A.
Dalpozzo R.
Locatelli M.
Melchiorre P.
Sambri L.
J. Org. Chem.
2006,
71:
9580
10a
Pope BM.
Sheu S.-J.
Stanley RL.
Tarbell DS.
Yamamoto Y.
J. Org. Chem.
1978,
43:
2410
10b
Dean CS.
Tarbell DS.
Friederang AW.
J. Org. Chem.
1970,
35:
3393
11
Gooßen L.
Döhring A.
Synlett
2004,
263
12
Bartoli G.
Bosco M.
Locatelli M.
Marcantoni E.
Melchiorre P.
Sambri L.
Org. Lett.
2005,
7:
427
13 By comparison, Gooßen obtained methyl 3-phenylpropan-oate(3ac ) in 93% yield after 16 hours at room temperature by mixing acid 1a , Moc2 O (2c ) and Mg(ClO4 )2 in nitromethane (4 mL) in the ratio 1:1.3:0.01, respectively.
14 The water molecules associated with the hydrated form of a Lewis acid catalyst allow the formation of a loose transition state, see: Chakraborti AK.
Sharma L.
Gulhane R.
.
Tetrahedron
2003,
59:
7661
15 In a blank run, ethanol and dicarbonate 2a were allowed to react in the presence of 10 mol% of magnesium chloride at room temperature and, after 48 hours, no appreciable amount of carbonate was detected.
For recent literature, see among others:
16a
Pasha MA.
Rizwana S.
Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem.
2005,
44:
420
16b
Jabbar S.
Banerjee S.
Asian J. Chem.
2002,
14:
1655
17
Bartoli G.
Boeglin J.
Bosco M.
Locatelli M.
Massaccesi M.
Melchiorre P.
Sambri L.
Adv. Synth. Catal.
2005,
347:
33 ; and references cited therein
18a
Staab HA.
Angew. Chem., Int. Ed. Engl.
1962,
1:
351
18b
Neises B.
Steglich W.
Angew. Chem., Int. Ed. Engl.
1978,
17:
522
18c
Mitsonobu O.
Synthesis
1981,
1
19 In contrast to magnesium perchlorate, which has a high activity for esterification (see ref. 9), magnesium chloride is unable to catalyze esterification between acid 1a and alcohol 4a in reaction times comparable with those reported in Table
[2 ]
.
20
Biermann U.
Metzger JO.
J. Am. Chem. Soc.
2004,
126:
10319
21
Armesto N.
Ferrero M.
Fernández S.
Gotor V.
J. Org. Chem.
2003,
68:
5784
22
Dhimitruka I.
SantaLucia J.
Org. Lett.
2006,
8:
47
23
Park YD.
Kim JJ.
Kim HK.
Cho SD.
Kang YJ.
Park KH.
Lee SG.
Yoon YJ.
Synth. Commun.
2005,
35:
371
24
Köster R.
Sporzynski A.
Schüßler W.
Bläser D.
Boese R.
Chem. Ber.
1994,
127:
1191
25
Zhang M.
Vedantham P.
Flynn DL.
Hanson PR.
J. Org. Chem.
2004,
69:
8340
26
Ashdown A.
Hey DH.
J. Chem. Soc.
1952,
1513
27
Sohn SS.
Bode JW.
Org. Lett.
2005,
7:
3873
28
Bromilow J.
Brownlee RTC.
Craik DJ.
Sadek M.
Taft RW.
J. Org. Chem.
1980,
45:
2429
29
Jones P.
Reddy ChK.
Knochel P.
Tetrahedron
1998,
54:
1471
30
Duclos S.
Evans HS.
Ward TR.
Helv. Chim. Acta
2001,
84:
3148
31
De Jeso B.
Droillard S.
Degueil-castaing M.
Saux A.
Maillard B.
Synth. Commun.
1988,
18:
1691
32
Davidson NE.
Rutherford TJ.
Botting NP.
Carbohydr. Res.
2001,
330:
295
33
Joshi BS.
Viswanathan N.
Gawad DH.
von Philipsborn W.
Helv. Chim. Acta
1975,
58:
1551
34
Black PJ.
Edwards MG.
Williams JMJ.
Eur. J. Org. Chem.
2006,
4367
35
Strazzolini P.
Dall’Arche MG.
Giumanini AG.
Tetrahedron Lett.
1998,
39:
9255
36
Wenkert E.
Guo M.
Lavilla R.
Porter B.
Ramachandran K.
Sheu JH.
J. Org. Chem.
1990,
55:
6203
37
Wannberg J.
Larhed M.
J. Org. Chem.
2003,
68:
5750
38
Baldwin JE.
Adlington RM.
Jain AU.
Kolhe JN.
Perry MWD.
Tetrahedron
1986,
42:
4247
39
Kumar V.
Sharma A.
Sinha AK.
Helv. Chim. Acta
2006,
89:
483
40
Crosignani S.
White PD.
Steinauer R.
Linclau B.
Org. Lett.
2003,
5:
853
41
Barton P.
Laws AP.
Page MI.
J. Chem. Soc., Perkin Trans. 2
1994,
2021
42
Miyashita M.
Shiina I.
Miyoshi S.
Mukaiyama T.
Bull. Chem. Soc. Jpn.
1993,
66:
1516
43
Venkateswarlu Y.
Reddy NS.
Ramesh P.
Rao MR.
Ram TS.
Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem.
1998,
37:
1264
44
Wills AJ.
Krishnan-Ghosh Y.
Balasubramanian S.
J. Org. Chem.
2002,
67:
6646
45
Seebach D.
Thaler A.
Blaser D.
Ko SY.
Helv. Chim. Acta
1991,
74:
1102
46
McElvain SM.
Curry MJ.
J. Am. Chem. Soc.
1948,
70:
3781
47
Bader AR.
Kontowicz AD.
J. Am. Chem. Soc.
1953,
75:
5416