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bohaizmr0

铜虫 (小有名气)

[交流] 求助翻译

Meldrum's acid (1, isopropylidene malonate or 2,2-dimethyl-
4,6-dioxo-1,3-dioxane), was first synthesized by
Meldrum in 19081 and the structure was incorrectly assigned
as the b-lactone of b-hydroxyisopropylmalonic
acid (b,b-dimethyl-b-propiolactone-a-carboxylic acid).2
It was only 40 years later that Davidson and Bernhard assigned
the correct structure.2 Meldrum’s acid has attracted
considerable attention due to its high acidity (pKa = 4.97)3
and rigid cyclic structure. Acylated derivatives (synthetic
equivalents of mixed ketenes) readily undergo alcoholysis
to give b-keto esters.4 Alkylidene derivatives are strong
electrophiles and can undergo Diels-Alder reactions with
high diasteroselectivity.5 This versatile tool is a key intermediate
for a large number of important building blocks
and there remains much to discover.

(A) Substituted g-pyrones 6 can be used in the synthesis of polyacetate-
and spiroketal-containing natural products and as cycloaddition
substrates for the construction of polycyclic systems.
Acylated Meldrum’s acid 3 reacts with a vinyl ether 4 with loss of
acetone and ring closure to the pyrone ring followed by decarboxylation.
The g-pyrone can then be obtained refluxing with a PTSA–
H2O mixture (40–85% yield). A variety of acid chlorides and vinyl
ethers can be used to prepare mono-, di- and trisubstituted
pyrones

(B) Optically active b-lactams 9 are obtained in excellent yields
(up to 93%) and with complete stereoselectivity from Meldrum’s
acid derivatives 7 and D2-thiazolines 8.7

(C) 2-Alkyl and 2-aryl 4-quinolones 14 can be prepared starting
from Meldrum’s acid 1 via their derivatives bisalkylthiolydine 10
(32–77% yield) and alkyl- and arylthioalkylidene 11 (52–90%
yield). Further reaction with arylamines 12 gives the arylaminoalkylidene
derivatives 13 (54–87% yield) which provide the
quinolone products upon heating (60–96% yield).8

(D) The reaction of Meldrum’s acid and its 5-substituted derivatives
15 with conjugated azoalkenes 16, in the presence of triethylamine,
produces the corresponding hydrazones 17 (71–98% yield)
via 1,4-conjugate addition. The hydrazone products then undergo
decarboxylative alcoholysis and simultaneous cyclization to give
3-unsubstituted and 3-monosubstituted 1-amino-1H-pyrrol-2-
(3H)-ones 18 (55–96% yield).9

(E) C-Dialkylation of Meldrum’s acid and 5-benzyl Meldrum’s
acid can be achieved through Mitsunobu dehydration using allylic
and arylmethyl alcohols as alkylating agents. With primary
alcohols, the alkylations always take place at the carbon bearing
the hydroxyl group. For secondary alcohols, a catalytic amount of
Pd(0) must be added to enhance the regioselectivity of C-alkylation
over O-alkylation. Using (Ph3P4)Pd(0) as a catalyst, the reaction
occurs specifically at the less hindered carbon, and the
configuration of the resulting double bound is always trans.10

(F) 5-Substituted 3-isoxazolols 27 can be synthesized in a threestep
procedure starting from Meldrum’s acid. After conversion
into the acylated derivative 24 (74–100% yield), aminolysis with
N,O-bis(tert-butoxycarbonyl)hydroxylamine (25) leads to the
N,O-diBoc b-keto hydroxamic acid 26 (53–91% yield). Treatment
with hydrochloric acid promotes cyclization to the desired product
(76–99% yield).11

(G) The pyrolysis of Meldrum’s acid derivatives in solution and in
gas phase takes place by loss of acetone and carbon dioxide to provide
ketene intermediates. In particular, methylene derivatives often
provide methyleneketenes, which act as substrates for internal
hydrogen transfer, leading to cyclization reactions. These cyclization
reactions are used for the efficient preparation of a diverse
range of cyclic compounds such as quinolinones, 3-hydroxythiophenes,
naphthols, azepin-3(2H)-ones or pyrrolizin-3-ones, initiated
respectively by 1,3-, 1,4-, 1,5-, 1,6 or 1,7-prototropic shifts.
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1楼 2009-03-28 13:24:34
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ekeyou

金虫 (小有名气)
这个工作量很大
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2楼2009-03-28 16:41:04
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jerry.lubo

木虫 (著名写手)
楼主你给的这个价估计没人看的上 呵呵
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3楼2009-03-28 17:27:10
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tanghuai

木虫 (正式写手)
★ ★
bohaizmr0(金币+2,VIP+0):谢谢你了！ 3-28 19:01
梅尔德拉姆酸(1-异丙叉异丙叉或2,2-二甲基-4,6-二氧基-1,3-二噁烷)在19081年首次由Meldrum合成，并且把其错误的认为是β-内酯(b,b-二甲基-b丙内酯-a-羧酸)。四十年后，Davidson和Bernhard就纠正了这一结构。梅尔德拉姆酸由于其强酸性(Pka=4.97)和刚性结构引起了广泛关注。酰化衍生物(合成的乙烯酮混合物)很容易醇解成b-氧代酯。亚烷基衍生物有很强的亲核力能发生D-A反应且具有高非对映选择性。这是用于许多重要结构单元的重要中间体，且需要进一步的研究。
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4楼2009-03-28 17:40:12
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tanghuai

木虫 (正式写手)
★ ★
bohaizmr0(金币+2,VIP+0):谢了 3-28 19:26
(B)合成具有旋光性的β-内酰胺类化合物9的产率很高(高达93%)，并且完整的保留了梅尔德拉姆酸衍生物7和D-2噻唑啉8.7的立体选择性。
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5楼2009-03-28 19:16:27
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tanghuai

木虫 (正式写手)
★ ★ ★
bohaizmr0(金币+3,VIP+0):太感谢了 3-29 08:17
(C)2-烷基和2-芳香基-4-喹诺酮化合物14可由梅尔德拉姆酸生成其衍生物10( 二烷基硫代亚烷基),产率是32-77%以及烷基和烷基硫代亚烷基化合物11，产率52-90%。进一步的反应是和芳香胺12反应生成芳香基氨基亚烷基衍生物13，产率54-87%。化合物13在加热条件下可生产喹诺酮8，产率60-96%。
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6楼2009-03-28 19:57:43
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