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Handbook of Functionalized Organometallics Applications in S

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460<br />

11 Polyfunctional Metal Carbenes for Organic Synthesis<br />

(CO) 5Cr<br />

OMe<br />

OTBDMS<br />

+<br />

OMe<br />

M= Cr: 35<br />

M= W: 36<br />

Me<br />

TBDMSO<br />

(CO) 5M<br />

A<br />

M= Cr: 31<br />

M= W: 32<br />

Me<br />

OMe<br />

TBDMSO<br />

C6H6, 19h<br />

Cr: 110ºC<br />

W: 75ºC<br />

Scheme 11.12 [2+2+1+1] (Two-alkyne) annulation towards the steroid skeleton.<br />

HO<br />

A B<br />

Me<br />

C D<br />

M= Cr: 33 (30%)<br />

M= W: 34 (51%)<br />

result<strong>in</strong>g carbazole 38 is converted <strong>in</strong>to the carbazoqu<strong>in</strong>oc<strong>in</strong> C 39 <strong>in</strong> a two-step<br />

oxidation/deprotection procedure (Scheme 11.13) [35].<br />

MeO<br />

N<br />

Bn<br />

Cr(CO) 5<br />

n-hept<br />

Me<br />

MeO<br />

N<br />

Bn<br />

37 38<br />

O<br />

N<br />

H<br />

39<br />

hν, CO<br />

THF<br />

65%<br />

O<br />

Me<br />

n-hept<br />

72%<br />

two steps<br />

OH<br />

Me<br />

n-hept<br />

Scheme 11.13 Photo<strong>in</strong>duced ortho-benzannulation towards carbazoqu<strong>in</strong>oc<strong>in</strong> C.

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