Triphosgene and DMAP as Mild Reagents for Chemoselective Dehydration of Tertiary Alcohols

Abstract

The utility of triphosgene and DMAP as mild reagents for chemoselective dehydration of tertiary alcohols is reported. Performed in dichloromethane at room temperature, this reaction is readily tolerated by a broad scope of substrates, yielding alkenes preferentially with the (E)-geometry. While formation of the Hofmann products is generally favored, a dramatic change in alkene selectivity toward the Zaitzev products is observed when the reaction is carried out in dichloroethane at reflux.

Evolution of a Synthetic Strategy for Garsubellin A

“…The Mukaiyama aldol reaction of 10 followed by dehydration using the combination of triphosgene and DMAP produced bis-enone 20 with high (Z)-selectivity (E : Z = 1 : 20). [23] The installation of a prenyl group was then carried out, once again, through the conjugate reduction-enolate trapping process using L-selectride and prenyl bromide, which took place only at the endogenous enone moiety with complete diastereoselectivity to give rise to 21 as a single isomer. The alkynylation was performed by treating 21 with KHMDS and allyl chloropropiolate using the Jørgensen protocol.…”

Syntheses of Bufospirostenin A and Ophiopogonol A by a Conformation-Controlled Transannular Prins Cyclization

“…With the cis-fused 5,7-bicyclic ring system in place, we moved on to finish the synthesis of 6. To this end, 11 was dehydrated with triphosgene and pyridine to give desired C5− C6 olefin 13 in 37% yield, 21 together with a 43% yield of undesired C4−C5 olefin 14. Notably, 14 could also be productively used by elaboration to a known intermediate 8g in three steps, thereby representing a formal synthesis of 6 (see Scheme S1 for details).…”

A Neutral FeCl3 Photocatalysis for C–C Bond Animation and Alkylation of Cyclic Alcohols

“…Data for NMR spectra were reported as follows: s = singlet, d = doublet, t = triplet, q = quartet, quint = quintet, dd = doublet of doublets, td = triplet of doublets, ddd = doublet of doublet of doublets, m = multiplet, coupling constant (Hz), and integration. The tertiary alcohols including 1f , 9 1h , 9 1v , 9 1g , 10 1i , 11 1j , 12 1u , 12 1k , 13 1l , 14 1m , 15 1n , 16 1o , 5a 1p , 5a 1r , 17 1t , 18 and 1y 19 are known and were prepared according to the literature.…”